en_obs-tn/content/05/03.md

father of many nations

Abram would have many descendants, and they would have their own lands and rule themselves. They and others would remember that Abram was their ancestor and would honor him.

I will be their God

Another way to say this is, "I will be the God that they will worship."

every male in your family

This could be translated as, "every boy and man in your family." This included Abram's servants and his descendants.