48. How old was Abraham when Ishmael was born?
86 years old
And Abram [Abraham] was fourscore and six years old, when Hagar bare Ishmael to Abram.
More than 135 years old
Abraham's father, Terah, was seventy years old when Abraham was born.
And Terah lived seventy years, and begat Abram.
Abraham didn't leave Haran until Terah died.
Our father Abraham ... dwelt in Haran: and from thence, when
his father was dead, he removed himself into this land.
And Terah died when he was 205.
And the days of Terah were two hundred and five years; and
Terah died in Haran. Genesis 11:32
Sometime after leaving Haran (when Abraham was at least 135 years old), Ishmael was born.
And he [Abraham] went in unto Hagar, and she conceived ...
And Hagar bare Abram a son: and Abram called his son's name, which Hagar bare, Ishmael.