Where in Torah is the first allusion regarding tehiat hametim (revival of the dead)? Please provide sources from Chazal to explain the allusion.
The Mishna implies rather strongly that this was the going assumption all along:
ואלו שאין להם חלק לעולם הבא האומר אין תחיית המתים מן התורה - And these are the ones who have no share in the world to come: he who says "the resuscitation of the dead is not from the Torah";...
The gemara in Sanhedrin 91b brings a number of verses that are sources to the derivation of the resurrection of the dead from the Torah, e.g.,
The Sages taught in a baraita with regard to the verse: “I will kill and I will bring to life.” One might have thought that it means that there will be death for one person and life for one other person, in the typical manner that the world operates. Therefore, the verse states: “I wounded and I will heal.” Just as wounding and healing take place in one person, so too, death and bringing back to life take place in one person. From here there is a response to those who say that there is no resurrection of the dead derived from the Torah.
It is taught in a baraita that Rabbi Meir said: From where is resurrection of the dead derived from the Torah? It is derived from a verse, as it is stated: “Then Moses and the children of Israel will sing this song to the Lord” (Exodus 15:1). It is not stated: Sang, in the verse; rather, the term “they will sing” is stated, indicating that Moses will come back to life and sing the song in the future. From here it is proved that resurrection of the dead is derived from the Torah.
On a similar note, you can say: “Then Joshua will build an altar to the Lord God of Israel on Mount Ebal” (Joshua 8:30). It is not stated: Built, in the verse; rather, the term “will build” is stated. From here, resurrection of the dead is derived from the Torah.
Rabbi Yehoshua ben Levi says: From where is resurrection of the dead derived from the Torah? It is derived from a verse, as it is stated: “Happy are they who dwell in Your house; they will yet praise You, Selah” (Psalms 84:5). It is not stated: They praised you, in the verse; rather, the term “they will praise you” is stated. From here, resurrection of the dead is derived from the Torah.
see the continuation for more
See also the gemara in Ketubot 111a
Rabbi Elazar said: The dead of the lands outside of Eretz Yisrael will not come alive and be resurrected in the future, as it is stated: “And I will set glory [tzvi] in the land of the living” (Ezekiel 26:20). This teaches that with regard to a land which contains My desire [tzivyoni], its dead will come alive; however, with regard to a land which does not contain My desire, i.e., outside of Eretz Yisrael, its dead will not come alive.
Rabbi Abba bar Memel raised an objection from a different verse: “Your dead shall live; my dead bodies shall arise” (Isaiah 26:19)
Rabbi Elazar said to Rabbi Abba bar Memel: My teacher, I teach it from a different verse, as it is stated: “He gives breath to the people upon it, and spirit to they who walk there” (Isaiah 42:5)
and see the discussion there.
The very first source for Techias Hameisim in the Torah is straight away when Adam first sinned and became Mortal (before that there was no need for Techias Hameisim) in Bereishis 3,19 G-d said to him: עד שובך אל האדמה כי ממנה לקחת כי עפר אתה ואל עפר תשוב - You shall die... Bereishis Rabba 20,10 explains:
אמר רבי שמעון בן יוחאי: מכאן רמז לתחיית המתים מן התורה, כי עפר אתה ואל עפר תלך לא נאמר, אלא תשוב:
Rabbi Shimon Bar Yochai said: from here is a hint of revival of the dead, it does not say :"you are made of earth and to Earth you shall go" i.e disintegrate for ever, rather it says "you shall return to Earth" i.e go back and live again