Cross reference
Genesis 21:5
5 And Abraham was a hundred years old, when his son Isaac was born unto him.
Genesis 17:17
17 Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born unto him that is a hundred years old? and shall Sarah, that is ninety years old, bear?
Genesis 17:1
1 And when Abram was ninety years old and nine, Jehovah appeared to Abram, and said unto him, I am God Almighty; walk before me, and be thou perfect.
Romans 4:19
19 And without being weakened in faith he considered his own body now as good as dead (he being about a hundred years old), and the deadness of Sarah's womb;