The answer is: Isaac

Genesis 21:3 - Isaac was the name of their son, meaning "he laughs," reflecting both Sarah's initial laughter and the joy his birth brought.

The story of Sarah and Abraham sharing the name Isaac for their son is rich with irony and depth! When we consider the meaning of Isaac, which is “he laughs,” it not only captures Sarah’s surprise during her advanced age but also encompasses the joy and wonder their miracle baby brought to their lives. Imagine the mix of disbelief and hilarity stirring within Sarah upon hearing she would bear a son—her laughter echoed by God's grace manifests in more than just a flippant moment.

Biblical drops of humor aren't foreign either. Similar bursts of laughter occur throughout the scriptures, like when Gideon's legs quaked in mid-battle—that's also laughter popping up in tension oddly transformed into joy! And, isn't it intriguing how characters like Abraham, Sarah’s husband, also had prominent transformations throughout their lives? Abraham, initially named Abram, experienced a pivotal change in direction after an encounter with the Divine. Name changes often symbolize a deeper, spiritual awakening in biblical tradition—note Peter going from Simon to rock-solid attendance in faith!

So, when we consider that joyful star of their timeline, Isaac isn’t merely a name. It embodies countless stories and laughs stitched into the tapestry of promise against all odds and illuminates how challenges can lead to the most extraordinary joy!