Why does Nedarim 37b contradict Shabbat 86a?
In Nedarim 37b, Children should not read a Torah passage [for the first time] on Shabbat :
Rather, with regard to Shabbat, this is the reason that children may not read a passage in the Bible for the first time on Shabbat, so that the fathers of the children will be at leisure to fulfill the mitzva of delighting in Shabbat. Teaching new material to their children would occupy more of their fathers’ time, limiting their opportunity to fulfill that mitzva. ( אֶלָּא גַּבֵּי שַׁבָּת הַיְינוּ טַעְמָא דְּאֵין קוֹרְאִין בַּתְּחִילָּה מִשּׁוּם דְּיִפְנוּ אֲבָהָתְהוֹן דְּיָנוֹקֵי לְמִצְוְתָא דְשַׁבְּתָא וְאִיבָּעֵית אֵימָא מִשּׁוּם דִּבְשַׁבְּתָא אָכְלִין וְשָׁתִין וְיַקִּיר עֲלֵיהוֹן עָלְמָא כִּדְאָמַר שְׁמוּאֵל שִׁינּוּי וֶסֶת תְּחִילַּת חוֹלִי מֵעַיִים )
Why then did Our Father give Torah [for the first time] to the children of Yisrael on Shabbat? - Stated in Shabbat 86a : Torah was given on Shabbat.
The Rabbis said this before Rav Pappa, and some say that Rav Pappa said this to Rava: Granted, Rabbi Elazar ben Azarya holds in accordance with the opinion of the Rabbis, who say with regard to the revelation at Sinai that Moses instituted separation between husbands and wives on the fifth day of the week. Since everyone agrees that the Torah was given on Shabbat, husbands and wives were separated for two days.
Nedarim 37b appears false, if Shabbat 86a is true. Nedarim does not apply to G-d, and ignores the example set by Our Father אָבִינוּ