The answer is: 90

Gen 17:17 / 21:5

When you think about Sarah giving birth at the age of 90, it’s just mind-blowing! Imagine the joy and, let’s face it, probably some skepticism that surrounded this monumental event. In Genesis 21:5, it clearly states that Sarah was indeed 90 when Isaac, whose name means "laughter," entered the world. That name fits perfectly, especially considering Sarah's laugh of disbelief back in Genesis 18 when she overheard the promise of her having a child at such an elderly age. Who could blame her?

This isn’t just a story about an improbable birth but also symbolizes deep hope and faith. Similar echoes can be found throughout the Scriptures, showing God's knack for surprising His people—think of Hannah, who prayed earnestly for a son and was eventually blessed with Samuel.

Also interesting: ancient Near Eastern culture highly valued offspring, and the narrative carefully deconstructs societal norms about age and fertility, challenging the typical expectations of motherhood.

It’s worth noting, too, that Sarah's journey of motherhood was transformative, not just for her but for all descendants of Isaac, ultimately leading to the lineage projected throughout biblical history. So behind this remarkable tale of a woman who laughed with joy and disbelief lies a profound lesson about endurance, promise, and unexpected blessings in life that we often overlook!