The story of Abraham, as told in Genesis, went through several layers of interactions with the Creator.
First, a special promise, Abraham's faith in response to the promise, a mistake in applying that faith to his situation, a special covenant (with a new name and a promise of a son with his wife Sarah), and a ring-side seat on God's judgement.
The narrative then moves on to the birth of Isaac, the promised son.
Despite all the build-up, the story of Isaac's birth doesn't contain much that is special.
However, it is sandwiched between Abraham's travels, dealings with other kings, and the family trouble between Sarah and Hagar.
Several parts of this story feel like repetitions of previous ones. Last time, it was the king of Egypt who desired Sarah. This time, it is Abimelech.
Both times, Abraham feared for his safety--or let Sarah continue the ruse used in previous times--to the point that a powerful man tried to take her as his wife.
Among the city-dwelling kings of that time, Abraham and his family are tribal nomads of the desert. Thus, some of their habits, and some of their lack of trust of powerful men, is in evidence.
It's a strange thing to read about. God previously spoke to Abraham, saying "I am your shield and protector". Yet Abraham, knowing the ways of kings, fears for his safety.
Yet God does act as protector and shield. Abimelech hears from God in a dream, and returns Sarah.
Trouble with Hagar crops up again. She is sent off with her son and some food. She reaches the end of her supply, and laments the death of herself and her son. God speaks to her, supplies her, and reminds her that her son will become leader of a great nation.
In all of this, we see God providing the child of promise. And protecting Abraham, even as Abraham and his family muddle through repeats of earlier problems.