The night after he got married, Daniel was deployed with Company B of the 72d Illinois Infantry; he served in the American Civil War. At this point, Whittle was not Christian, but during the war, he lost his right arm, and spent several weeks in a hospital. During this time he found a New Testament, and it was the only book on hand and he wanted to read something. Shortly after, a hospital orderly woke him and said a dying prisoner wanted someone to pray with him. Whittle demurred, but the orderly said, “But I thought you were a Christian; I have seen you reading your Bible.” Whittle then agreed to go. He recorded what took place at the dying youth’s bed side:
I dropped on my knees and held the boy’s hand in mine. In a few broken words I confessed my sins and asked Christ to forgive me. I believed right there that He did forgive me. I then prayed earnestly for the boy. He became quiet and pressed my hand as I prayed and pleaded God’s promises. When I arose from my knees, he was dead. A look of peace had come over his troubled face, and I cannot but believe that God, who used him to bring me to the Savior, used me to lead him to trust Christ’s precious blood and find pardon. I hope to meet him in heaven.
Whittle was brevetted with the rank of major at the end of the war, that is why among hymnologist, he is called Major Whittle.
He settled in Chicago and started to work very close with D. L. Moody, who encouraged him to do evangelism work. Indeed, he preached with his hymns. His most popular hymn among Christians is “I Know Whom I Have Believed.”
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 us of sin,
Revealing Jesus through the Word,
Creating faith in Him.
I know not what of good or ill
May be reserved for me,
Of weary ways or golden days,
Before His face I see.
I know not when my Lord may come,
At night or noonday fair,
Nor if I walk the vale with Him,
Or meet Him in the air.
But I know Whom I have believèd,
And am persuaded that He is able
To keep that which I’ve committed
Unto Him against that day.
In His service.