5 Abraham was one hundred years old when his son, Isaac, was born to him.
Genesis 21:5 Cross References - NHEB
Genesis 17:1
1 When Abram was ninety-nine years old, the LORD appeared to Abram, and said to him, "I am El Shaddai. Walk before me, and be blameless.
Genesis 17:17
17 Then Abraham fell on his face, and laughed, and said in his heart, "Will a child be born to him who is one hundred years old? Will Sarah, who is ninety years old, give birth?"
Romans 4:19
19 And not being weak in faith, he considered his own body, which was as good as dead (he being about a hundred years old), and the deadness of Sarah's womb.