5 Now Abraham was a hundred years old,––when Isaac his son was born to him.
Genesis 21:5 Cross References - Rotherham
Genesis 17:1
1 And it came to pass that, when Abram was ninety and nine years old, Yahweh appeared unto Abram, and said unto him, I, am GOD Almighty,––Walk thou before me, and become thou blameless:
Genesis 17:17
17 And Abraham fell on his face, and laughed,––and said in his heart, To one a hundred years old, shall a child be born? And shall, even Sarah, who is ninety years old, give birth?
Romans 4:19
19 And, without becoming weak in his faith, he attentively considered his own body, already deadened––he being a hundred years old, the deadening also of Sarah’s womb;