A man may not refrain from [the mitzvah of] being fruitful and multiplying, unless he has children —- Beis Shammai say: Two males; but Beis Hillel say: A male and a female, as it is stated (Genesis 5:2): “He created them male and female.”  One who married a woman and remained with her ten years, but she did not bear children, is not permitted to refrain [from the fulfilling the mitzvah]. [If] he divorced her, she may marry another, and the second one may remain with her for ten years. If she miscarried, he counts from the time of her miscarriage.  The man is commanded to be fruitful and multiply, but not the woman. R' Yochanan ben Beroka says: Concerning both of them it is stated (Genesis 1:28): “And God blessed them and said to them be fruitful and multiply.”