"Choose (good women) for your sperms, for ethics pass from fathers to children

It has been reported from the Prophet, may Allah bless him and his family, that a man belonged to the Ansars came to him and said to him: "O Allah's Apostle, this is my cousin. I am so-and-so, son of so-and-so (counting ten forefathers). She is the daughter of so-and-so (counting ten forefathers); there is no Abyssinian in her lineage nor in mine, but she has given birth to this Abyssinian." Allah's Apostle, may Allah bless him and his family, bowed his head and then he raise it and said: "Surely you have ninety-nine races, and she has ninety-nine races. When the races come together, they move, and each race of them asks Allah, the Great and Almighty, to let its like to go to it. Stand up! He is your son; he has not come to you except through a race of yours or of hers."
The man left taking his wife and his son by the hand. In another tradition, (the Prophet) said: "Choose (good women) for your sperms, for ethics pass from fathers to children (al-'iriq dassas)."


Reference : THE LIFE OF IMAM MUSA BIN JA'FAR AL-KAZIM