The answer is: 90

Gen 17:17 / 21:5

Sarah's life is full of remarkable moments, but the birth of her son Isaac at the astonishing age of 90 is often highlighted as one of the fascinating miracles in the Bible. God’s promise to Abraham was intertwined with Sarah's destiny, illustrating that extraordinary things can happen even when circumstances look bleak. Imagine waiting decades for a child and finally seeing that dream materialize in what most would consider the twilight years!

It’s intriguing to note that Sarah's story isn’t an isolated incident in the Bible. There have been several women who were said to bear children later in life, including Hannah, who gave birth to Samuel, and Elizabeth, who became the mother of John the Baptist. These narratives echo God's continuous theme of hope and promise, showcasing that divine potential knows no age limits.

In essence, the birth of Isaac acts as a powerful symbol of laughter and joy—an appropriate descriptor since "Isaac" actually means "laughter" in Hebrew. This birth narrative also resonates with modern discussions on fertility and parenthood, showing that while timing is important, implications of life's purpose and divine timing are often beyond human comprehension. Such stories invite reflection on faith and destiny and encourage individuals to consider that life often holds sweet surprises, well beyond expected timelines.