Yevamot 62 - How many children must a man have?
A man is obligated to fulfill the commandment to be fruitful and multiply. How many children are sufficient? - Two sons - these are the words of Beit Shammai. What is their logic? Moses had two sons, and after that he abstained from having relations with his wife. However, Beit Hillel say that a man must have a son and a daughter. Why? - Just like God created a male and a female, so is this mitzvah. Incidentally, all agree that it is not proper for a man to be without a wife, even if he has fulfilled the obligation to be fruitful, because the Torah said, " It's not good for a man to be alone ."
Why don't Beit Shammai learn from the creation of the world, just as Beit Hillel do? - They answer that there it was impossible to do otherwise: Eve had to be created in order that Adam has a wife; however, in our context, if a man has two sons, there are many women in the world that they can marry.
Then why don't Beit Hillel learn from the life of Moses, as Beit Shammai do? - They answer that Moses' situation was unique, and he separated from his wife on the his accord. What was his logic? He reasoned thus: if the children of Israel, with whom God spoke only one time, while giving the Torah, had to stay away from their wives, then I (Moses), with whom God speaks at all times, how much more so I have to stay away from my wife? - and God later agreed with him, saying " Tell them to go back to their houses (wives) ," which we understand to imply, "But you are correct in staying here with Me."
Actually, there were three cases where Moses did things on his own accord, and God later agreed. Another one was breaking the Tablets. Moses reasoned: if the Passover offerings - which is only one commandment in the Torah - is forbidden to one who is a "estranged" from the Torah, then the whole Torah is of course forbidden to the Jews who worship a Golden Calf. God later agreed, saying " Tablets, which you broke ." The word "which," "asher," can be understood as "yasher koach" - correct that you did it.
Art: Mrs. Arthur Knowles and her Two Sons by John Singer Sargent