Genesis 16:16
And Abram was fourscore and six years old, when Hagar bare Ishmael to Abram.
Cross-reference
Genesis 17:1
Historical context
In Genesis 17:1, thirteen years have passed — God appears to Abram at 99, resuming covenant speech after the silence following Ishmael's birth.
Galatians 4:24
Allusion
In Galatians 4:24, Paul identifies Hagar — Ishmael's mother referenced here — as an allegory for the Sinai covenant of bondage.