“My God, you spoke to me, your servant. You made it clear that you would make my family a family of kings. That is why I am being so bold—that is why I am asking you to do these things.
Lord, you have been kind enough to bless my family.You were kind enough to promise that my family will serve you forever. Lord, you yourself blessed my family, so my family really will be blessed forever!”
Those two things cannot change. God cannot lie when he says something and he cannot lie when he makes a vow. So those things give great comfort to us who came to God for safety. Those two things give us comfort and strength to continue in the hope that God gives us.