The answer is: Psalm 90

Psalm 90 - This psalm, attributed to Moses, reflects on the brevity of human life and God’s eternal nature. It contrasts the fleeting existence of man with God’s everlasting presence. Interestingly, it serves as a lament but also calls for wisdom (90:12), paralleling themes found in Ecclesiastes regarding the meaning of life.

Psalm 90, often dubbed “A Prayer of Moses,” is a profound reflection on the human experience nestled within the poetry of the Psalms. Interestingly, Moses, a compelling figure in the biblical narrative, is traditionally thought to have penned this piece during the Israelite’s sojourn in the wilderness, highlighting his intimate connection with the divine during times of challenge.

The psalm opens with a beautiful acknowledgment of God's eternal nature: "Before the mountains were born... you are God" (90:2). This sets the stage for a deep exploration of human transience. The heart of Psalm 90 resonates with many—a contemplation that echoes throughout scripture, especially in books like Ecclesiastes, where the futility of earthly pursuits is startlingly laid bare. The poignant line urging readers to “number our days” (90:12) pushes us to take every moment seriously, fostering a wisdom that encourages meaningful living amidst life’s fleeting nature.

One fun trivia nugget? This psalm also includes a direct insight into mortality numbers, where the span of life is termed “70 years, or 80 for those who are strong” (90:10)—mocking our alarm at aging or life stages with its radical honesty, and yet a glimmer of hope flows through it, reminding readers of the beauty that can arise from a life well-lived, if only we seek to understand our days meaningfully. What's more astounding: generations have invoked this prayer to stitch the fabric of faith, reflecting on life’s rhythm and divinity in varying contexts. What a marvelous legacy!