"Blessed Assurance" is a well-known Christian hymn.

The organ was incomplete, so Mrs. Knapp, using the piano, played a new melody she had just composed.

", Crosby replied, "Blessed assurance; Jesus is mine.

"[1] The hymn appeared in the July 1873 issue of Palmer's Guide to Holiness and Revival Miscellany, a magazine printed by Dr. and Mrs. W. C. Palmer of 14 Bible House, New York City.

The popular song reflects Crosby's walk of faith, as expressed by the apostle Paul in Philippians "For to me, to live is Christ and to die is gain" (Philippians 1:21).Because of Crosby's lyrics, the tune is now called "Blessed Assurance".