9 explicated conclusion of rama's recommended practice
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See Mishna in Yadaym 3, 5.

The Gemara in Massechet Megila 7A exposed a Machloket:

Rab Judah said in the name of Samuel; [The scroll] of Esther does not make the hands unclean...
{This is a Machloket tanaym see here Rabbi Shim'on's opinion R`Simeon vs. Rq Josuah} R`Simeon says that Koheleth is one of those matters in regard to which Beth Shammai were more lenient and Beth Hillel more stringent, but Ruth and the Song of Songs and Esther [certainly] make the hands unclean'! - Samuel concurred with R`Joshua.
If the Gemara says that he concurred with R"J, it is a sign that the Halacha is not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (in the left column of the page) and see here in the right top concerning touching naked Megilat Ester.

See Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 and see Magen Avraham (S.A. O.C. 147 S.K. 1) says that Megilot are as Sefer Tora, and that Rambam do not follow the opinion of Shmuel in Gemara cited above.

 

The Rama, says "ולא נהגו כן" and the Mishna Brura, and Beur Halacha, explains that some Poskim allowed to touching Sefer tora) when the person washed ons'e hands (Mordechay in name of Raavia, Rashba, Tosfot[1][1]). But there is no hilightment of a difference between S.T. and Megilah

 

Conclusion

  1. weWe found no differences in Rishonim between Megila and S.T,
  2. But we found a Machloket in both, some rishonim allow to touching S.T and Megila with cleaned hands, and some others prohibited.
  3. It seems that the minhag cited in the OP and in Rema isrecommends a Psharacompromise between the 2 opinions, usingrelying on the kulaleniency of allowing touching after washing for Megila and the Chumra(and other books of Nakh), but being stringent for S.Ta Sefer Torah.


[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila

See Mishna in Yadaym 3, 5.

The Gemara in Massechet Megila 7A exposed a Machloket:

Rab Judah said in the name of Samuel; [The scroll] of Esther does not make the hands unclean...
{This is a Machloket tanaym see here Rabbi Shim'on's opinion R`Simeon vs. Rq Josuah} R`Simeon says that Koheleth is one of those matters in regard to which Beth Shammai were more lenient and Beth Hillel more stringent, but Ruth and the Song of Songs and Esther [certainly] make the hands unclean'! - Samuel concurred with R`Joshua.
If the Gemara says that he concurred with R"J, it is a sign that the Halacha is not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (in the left column of the page) and see here in the right top concerning touching naked Megilat Ester.

See Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 and see Magen Avraham (S.A. O.C. 147 S.K. 1) says that Megilot are as Sefer Tora, and that Rambam do not follow the opinion of Shmuel in Gemara cited above.

The Rama, says "ולא נהגו כן" and the Mishna Brura, and Beur Halacha, explains that some Poskim allowed to touching Sefer tora) when the person washed ons'e hands (Mordechay in name of Raavia, Rashba, Tosfot[1]). But there is no hilightment of a difference between S.T. and Megilah

 

Conclusion

  1. we found no differences in Rishonim between Megila and S.T,
  2. But we found a Machloket in both, some rishonim allow to touching S.T and Megila with cleaned hands, and some others prohibited.
  3. It seems that the minhag cited in the OP and in Rema is a Pshara between the 2 opinions, using the kula for Megila and the Chumra for S.T.


[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila

See Mishna in Yadaym 3, 5.

The Gemara in Massechet Megila 7A exposed a Machloket:

Rab Judah said in the name of Samuel; [The scroll] of Esther does not make the hands unclean...
{This is a Machloket tanaym see here Rabbi Shim'on's opinion R`Simeon vs. Rq Josuah} R`Simeon says that Koheleth is one of those matters in regard to which Beth Shammai were more lenient and Beth Hillel more stringent, but Ruth and the Song of Songs and Esther [certainly] make the hands unclean'! - Samuel concurred with R`Joshua.
If the Gemara says that he concurred with R"J, it is a sign that the Halacha is not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (in the left column of the page) and see here in the right top concerning touching naked Megilat Ester.

See Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 and see Magen Avraham (S.A. O.C. 147 S.K. 1) says that Megilot are as Sefer Tora, and that Rambam do not follow the opinion of Shmuel in Gemara cited above.

 

The Rama, says "ולא נהגו כן" and the Mishna Brura, and Beur Halacha, explains that some Poskim allowed to touching Sefer tora) when the person washed ons'e hands (Mordechay in name of Raavia, Rashba, Tosfot[1]). But there is no hilightment of a difference between S.T. and Megilah

Conclusion

  1. We found no differences in Rishonim between Megila and S.T,
  2. But we found a Machloket in both, some rishonim allow to touching S.T and Megila with cleaned hands, and some others prohibited.
  3. It seems that the Rema recommends a compromise between the 2 opinions, relying on the leniency of allowing touching after washing for Megila (and other books of Nakh), but being stringent for a Sefer Torah.


[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila

8 naki nachon barur
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See Mishna in Yadaym 3, 5. See Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 See Magen Avraham (S.A. O.C. 147 S.K. 1) says that Megilot are as Sefer Tora
The

The Gemara in Massechet Megila 7A exposed a Machloket:

  
Rab Judah said in the name of Samuel; [The scroll] of Esther does not make the hands unclean...
{This is a Machloket tanaym see here Rabbi Shim'on's opinion R`Simeon vs. Rq Josuah} R`Simeon says that Koheleth is one of those matters in regard to which Beth Shammai were more lenient and Beth Hillel more stringent, but Ruth and the Song of Songs and Esther [certainly] make the hands unclean'! - Samuel concurred with R`Joshua.
If the Gemara says that he concurred with R"J, it is a sign that the Halacha is not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (in the left column of the page) and see here in the right top concerning touching naked Megilat Ester.

If the GemaraSee Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 and see Magen Avraham (S.A. O.C. 147 S.K. 1) says that he concurred with R"JMegilot are as Sefer Tora, it is a signand that the Halacha isRambam do not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (infollow the left columnopinion of the page) and see hereShmuel in the right top concerning touching naked Megilat EsterGemara cited above.
The

The Rama, says "ולא נהגו כן" and the Mishna Brura, and Beur Halacha, explains that some Poskim allowed to touching Sefer tora) when the person washed ons'e hands (Mordechay in name of Raavia, Rashba, Tosfot[1]). But there is no hilightment of a difference between S.T. and Megilah   

Conclusion,

Conclusion

  1. we found no differences in Rishonim between Megila and S.T,
  2. But we found a Machloket in both, some rishonim allow to touching S.T and Megila with cleaned hands, and some others prohibited.
  3.  
  4. It seems that the minhag cited in the OP and in Rema is a Pshara between the 2 opinions, using the kula for Megila and the Chumra for S.T.


[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila

See Mishna in Yadaym 3, 5. See Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 See Magen Avraham (S.A. O.C. 147 S.K. 1) says that Megilot are as Sefer Tora
The Gemara in Massechet Megila 7A exposed a Machloket:

 
Rab Judah said in the name of Samuel; [The scroll] of Esther does not make the hands unclean...
{This is a Machloket tanaym see here Rabbi Shim'on's opinion R`Simeon vs. Rq Josuah} R`Simeon says that Koheleth is one of those matters in regard to which Beth Shammai were more lenient and Beth Hillel more stringent, but Ruth and the Song of Songs and Esther [certainly] make the hands unclean'! - Samuel concurred with R`Joshua.

If the Gemara says that he concurred with R"J, it is a sign that the Halacha is not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (in the left column of the page) and see here in the right top concerning touching naked Megilat Ester.
The Rama, says "ולא נהגו כן" and the Mishna Brura, and Beur Halacha, explains that some Poskim allowed to touching Sefer tora) when the person washed ons'e hands (Mordechay in name of Raavia, Rashba, Tosfot[1]). But there is no hilightment of a difference between S.T. and Megilah  

Conclusion,

  1. we found no differences in Rishonim between Megila and S.T,
  2. But we found a Machloket in both, some rishonim allow to touching S.T and Megila with cleaned hands, and some others prohibited.
  3. It seems that the minhag cited in the OP and in Rema is a Pshara between the 2 opinions, using the kula for Megila and the Chumra for S.T.


[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila

See Mishna in Yadaym 3, 5.

The Gemara in Massechet Megila 7A exposed a Machloket: 

Rab Judah said in the name of Samuel; [The scroll] of Esther does not make the hands unclean...
{This is a Machloket tanaym see here Rabbi Shim'on's opinion R`Simeon vs. Rq Josuah} R`Simeon says that Koheleth is one of those matters in regard to which Beth Shammai were more lenient and Beth Hillel more stringent, but Ruth and the Song of Songs and Esther [certainly] make the hands unclean'! - Samuel concurred with R`Joshua.
If the Gemara says that he concurred with R"J, it is a sign that the Halacha is not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (in the left column of the page) and see here in the right top concerning touching naked Megilat Ester.

See Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 and see Magen Avraham (S.A. O.C. 147 S.K. 1) says that Megilot are as Sefer Tora, and that Rambam do not follow the opinion of Shmuel in Gemara cited above.

The Rama, says "ולא נהגו כן" and the Mishna Brura, and Beur Halacha, explains that some Poskim allowed to touching Sefer tora) when the person washed ons'e hands (Mordechay in name of Raavia, Rashba, Tosfot[1]). But there is no hilightment of a difference between S.T. and Megilah 

Conclusion

  1. we found no differences in Rishonim between Megila and S.T,
  2. But we found a Machloket in both, some rishonim allow to touching S.T and Megila with cleaned hands, and some others prohibited.
  3.  
  4. It seems that the minhag cited in the OP and in Rema is a Pshara between the 2 opinions, using the kula for Megila and the Chumra for S.T.


[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila

7 correction accurate
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See Mishna in Yadaym 3, 5. See Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 See Magen Avraham (S.A. O.C. 147 S.K. 1) says that Megilot are as Sefer Tora
The Gemara in Massechet Megila 7A exposed a Machloket:

Rab Judah said in the name of Samuel; [The scroll] of Esther does not make the hands unclean...
{This is a Machloket tanaym see here Rabbi Shim'on's opinion R`Simeon vs. Rq Josuah} R`Simeon says that Koheleth is one of those matters in regard to which Beth Shammai were more lenient and Beth Hillel more stringent, but Ruth and the Song of Songs and Esther [certainly] make the hands unclean'! - Samuel concurred with R`Joshua.

If the Gemara says that he concurred with R"J, it is a sign that the Halacha is not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (in the left column of the page) and see here in the right top concerning touching naked Megilat Ester.
The Rama, says "ולא נהגו כן" and the Mishna Brura, and Beur Halacha, explains that some Poskim allowed to touching Sefer tora) when the person washed ons'e hands (Mordechay in name of Raavia, Rashba, Tosfot[1]). But there is no hilightment of a difference between S.T. and Megilah Conclusion, we found no differences in Rishonim between Megila and S.T, but some allowing opinions about both was practised concerning the Megila.


[1] Tosfot says in conclusion that after netilat yadaym

Conclusion

, it is prohibited to touch sefer Tora as Megila

  1. we found no differences in Rishonim between Megila and S.T,
  2. But we found a Machloket in both, some rishonim allow to touching S.T and Megila with cleaned hands, and some others prohibited.
  3. It seems that the minhag cited in the OP and in Rema is a Pshara between the 2 opinions, using the kula for Megila and the Chumra for S.T.


[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila

See Mishna in Yadaym 3, 5. See Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 See Magen Avraham (S.A. O.C. 147 S.K. 1) says that Megilot are as Sefer Tora
The Gemara in Massechet Megila 7A exposed a Machloket:

Rab Judah said in the name of Samuel; [The scroll] of Esther does not make the hands unclean...
{This is a Machloket tanaym see here Rabbi Shim'on's opinion R`Simeon vs. Rq Josuah} R`Simeon says that Koheleth is one of those matters in regard to which Beth Shammai were more lenient and Beth Hillel more stringent, but Ruth and the Song of Songs and Esther [certainly] make the hands unclean'! - Samuel concurred with R`Joshua.

If the Gemara says that he concurred with R"J, it is a sign that the Halacha is not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (in the left column of the page) and see here in the right top concerning touching naked Megilat Ester.
The Rama, says "ולא נהגו כן" and the Mishna Brura, and Beur Halacha, explains that some Poskim allowed to touching Sefer tora) when the person washed ons'e hands (Mordechay in name of Raavia, Rashba, Tosfot[1]). But there is no hilightment of a difference between S.T. and Megilah Conclusion, we found no differences in Rishonim between Megila and S.T, but some allowing opinions about both was practised concerning the Megila.


[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila

See Mishna in Yadaym 3, 5. See Rambam Sefer Taharot, hilchot Avot haTum'a 9, 6 See Magen Avraham (S.A. O.C. 147 S.K. 1) says that Megilot are as Sefer Tora
The Gemara in Massechet Megila 7A exposed a Machloket:

Rab Judah said in the name of Samuel; [The scroll] of Esther does not make the hands unclean...
{This is a Machloket tanaym see here Rabbi Shim'on's opinion R`Simeon vs. Rq Josuah} R`Simeon says that Koheleth is one of those matters in regard to which Beth Shammai were more lenient and Beth Hillel more stringent, but Ruth and the Song of Songs and Esther [certainly] make the hands unclean'! - Samuel concurred with R`Joshua.

If the Gemara says that he concurred with R"J, it is a sign that the Halacha is not as he says, but as R Shimon says. See Tshuvat Rav Hay Gaon here (in the left column of the page) and see here in the right top concerning touching naked Megilat Ester.
The Rama, says "ולא נהגו כן" and the Mishna Brura, and Beur Halacha, explains that some Poskim allowed to touching Sefer tora) when the person washed ons'e hands (Mordechay in name of Raavia, Rashba, Tosfot[1]). But there is no hilightment of a difference between S.T. and Megilah

Conclusion

,
  1. we found no differences in Rishonim between Megila and S.T,
  2. But we found a Machloket in both, some rishonim allow to touching S.T and Megila with cleaned hands, and some others prohibited.
  3. It seems that the minhag cited in the OP and in Rema is a Pshara between the 2 opinions, using the kula for Megila and the Chumra for S.T.


[1] Tosfot says in conclusion that after netilat yadaym, it is prohibited to touch sefer Tora as Megila

6 correction of error.
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