Within these three chapters, Abram gets renamed Abraham. You know, the great patriarch of Judaism. He also does quite a bit of disbelieving of the Lord, and learns about circumcision.
God comes to Abram in a vision and tells him that he will have seed as the number of the stars (Gen. 15:1-5). (Just as He did in Gen. 14:14-17, and in Gen. 12:1-3.) Abram points out that the closest thing he has to an heir is Eliezer of Damascus, his steward; but he believes what the Lord tells him.
Then, God tells him that he will give Abram certain land to inherit. What does Abram do? Asks for a sign, of course. Because a vision of God isn’t good enough, apparently. (Gen. 15:7-9)
So, God instructed him to make a particular sacrifice. The next night, Abram fell into a deep sleep and had another vision, in which God told him that Abram’s descendants would be slaves in someone else’s land for 400 years, but would emerge with great wealth. (Gen. 15:9-21)
Since the first vision apparently wasn’t enough for Abram, God demanded a sacrifice, then gave Abram another vision.
If the first vision was not a sign, why would a second vision be a sign?
Sarai was barren, so she sent her Egyptian handmaid, Hagar, to Abram that Hagar might bear him an heir. Once Hagar got pregnant, she no longer respected Sarai, who regretted her choice and explained the situation to Abram. Abram told her, “She’s your maid, deal with her as you wish.” Sarai did, and caused Hagar to flee. (Gen. 16:1-6)
Fortunately, the Angel of the Lord found Hagar out by a spring in the wilderness and told her to go back to Sarai and submit to her, and as a result her seed would be innumerable. The angel also instructed Sarai to name her son Ishmael, and told her that he would be a wild man. (Gen. 16:7-16) Thus, Abram received an heir, Ishmael, at the age of 86.
Thirteen years later, when Abram was 99 years old, the Lord appeared to him again! He told him to change his name to Abraham, for he would be a father of many nations. As His covenant, the Lord told Abraham to circumcise every male of his people; not just his descendants, but also slaves bought from others. Anyone not circumcised would be cast out. (Gen. 17:1-14)
Why do you think God chose genital mutilation as the sign of his covenant? Why not a branding or a tattoo? Or do you think God was concerned about hygiene and the potential for urethral infections?
God then told Abraham to rename Sarai “Sarah”, and that she would be a mother of nations. Abraham’s reaction? He laughed, and thought that it was silly to suggest that he, at 100, and his wife, at 90, would bear children! (Gen. 17:15-17)
If God were standing before you and making you promises, do you think you would laugh and think Him silly?
Or do you think Abram didn’t think of God as modern Christians do, as the all-powerful creator of the universe, able to do anything He desires?
God told Abraham that Sarah would indeed bear him a son, to be named Isaac; He also promised that Ishmael would be exceedingly fruitful. Then He left, and Abraham began circumcising all the male humans of his household, slicing off part of their foreskins. (Gen. 18:19-27)
What must life have been like in those days? God appeared only to Abraham, yet all the men and boys in his household allowed Abraham to mutilate their genitals. Would you allow an old man to come at you with a sharp rock after he’d had a vision in the wilderness?
Why not? Do you not have faith in the Lord?