Genesis 21:1

“Now Sarah my master’s wife bore a son to my master in her old age, and he has given him all that he has.

Then they arose early in the morning and worshiped before Yahweh and turned back and came to their house in Ramah. And Elkanah knew Hannah his wife, and Yahweh remembered her.

Yahweh indeed visited Hannah; and she conceived and gave birth to three sons and two daughters. And the young boy Samuel grew before Yahweh.

But the son by the servant-woman had been born according to the flesh, while the son by the free woman through the promise.

Isaac Is Born