The answer is: 90

Genesis 17:17 - Sarah was 90 years old when she gave birth to Isaac, showing that God's promise came true despite what seemed impossible by human standards.

Imagine a 90-year-old woman becoming a mother—it's a story that sounds more like the plot of a comedy than reality! Yet, in the story of Sarah and Isaac, we get a deep glimpse into the concept of divine possibility. Sarah's age puts her well beyond the average childbearing years, making this miracle fully come alive when it’s framed within context. The birth of Isaac, with his very name meaning "laughter," conveys both a sense of joy and the absurdity of big miracles happening to ordinary people.

What's fascinating is that this miracle isn’t just an isolated incident; many biblical characters experience extraordinary births. Take the births of Samuel and even John the Baptist, all narratives highlighting themes of Divine intervention when human capabilities dim. These echoes in biblical storytelling amplify the message that life, hope, and the unfolding of plans can proceed in unexpected ways. Isn’t it courageous how these tales challenge our understanding of dynamics such as age and potential?

Also noteworthy is the significance of faith throughout these interactions. Here’s an inspiring detail: Sarah laughed not because she doubted, but perhaps because she was simultaneously delighted and astonished at how far God's promise would stretch. Each individual's life's journey across the Bible unveils a touch of the miraculous, suggesting a timeless message: the beauty in believing beyond life's limits. So the story of Sarah continually lingers, beckoning us to envision a world where the impossible is possible!