What are the ideal ages when a child will listen to his/her parents? Is a grandfather obligated to teach his grandson Torah? One should split one's learning - a third Torah, a third Mishna, and a third Talmud - this is derived from the word v'shinantam. The early soferim would count all the letters in the Torah and knew which letter/word/verse was the middle one. This capability ceased to exist as the rabbis were no longer certain of which words were written with or without yuds and vavs and where to divide verses. V'shinantam is also used to teach that one should understand the Torah that one has learned very well. V'shinantam is also used to teach that learning Torah is an elixir to protect from the evil inclination.  The Gemara continues to discuss the various other obligations a man has toward his son (that were mentioned in the braita in Kiddushin 29) - marrying him off, teaching him a trade, and how to swim. From where are each of these obligations derived? Mitzvot that are incumbent on children to do for their parents, men and women are obligated equally. This is derived from the commandment to fear one's parents. However, a married woman has an exception if her husband's needs conflict with her parent's needs and he insists on his needs superseding theirs.