How long did Abraham wait for God's promise to be fulfilled?
Abraham waited nearly 50 years from when God first gave the promises in Ur until the promised child was born when Abraham was 100 years old. The promise began around age 50, he left Haran at 75, and fulfillment came at 100.
Les teaches that Abraham's whole promise from God began back in Ur when he was probably about 50 years old. He didn't leave Haran until he was 75, and he didn't even receive Ishmael until he was near 80. Finally, when Abraham was 100 and Sarah was 90, God performed, and the promises became fulfilled. Les points out that Abraham had almost 50 years to sweat the promises while nothing happened, and after 50 years of promises, here comes the child. Les uses this to show that God's wheels grind slowly but surely, and that we must sit back and trust His way rather than assuming He isn't doing anything.