The title, "I Know Whom I Have Believed," are words of Paul in 2 Timothy 1:12:

Chorus:

But I know whom I have believed, and am persuaded that He is able

To keep that which I've committed, unto Him against that day.

As a POW during the Civil War, Daniel Whittle began reading the New Testament his mother had given him as he marched off to war.  A guard saw him reading the Bible, and asked if he would pray with a dying soldier.  Even though he was learning himself, Daniel felt compassion for the soldier, and prayed with him, sensing peace coming to the soldier.

After the war, Whittle became a successful businessman.  He met D. L. Moody, and began preaching in evangelistic services in 1873.  For a quarter of a century, he led revivals throughout the United States, and wrote many hymns, including "Showers of Blessing" and "Moment by Moment."

The verses to the song are:

I know not why God's wondrous grace to me He hath made known,

Nor why, unworthy, Christ in love redeemed me for His own.

I know not how this saving faith to me He did impart,

Nor how believing in His Word wrought peace within my heart.

I know not how the Spirit moves, convincing men of sin,

Revealing Jesus through the Word, creating faith in Him.

I know not when my Lord may come, at night or noonday fair,

Nor if I'll walk the vale with Him, or "meet Him in the air."