Blessed Assurance" is a typical gospel hymn of the late nineteenth century. It is simple, truly evangelical in spirit, and has an emotional appeal that comes from its rousing tune and from the personal experience described in the text. It is a fine testimonial hymn of praise to Christ for his work of redemption (st. 1), for the Spirit's work of sanctification (st. 2), and for the joy of serving Jesus (st. 3).
Psalter Hymnal Handbook
This is the testimony of Heidelberg Catechism, Lord’s Day 1, Question and Answer 1 in song! “I belong, body and soul, in life and death, to my faithful Savior Jesus Christ” and “because I belong to him, Christ, by His Holy Spirit, assures me of eternal life and makes me wholeheartedly willing and ready from now on to live for him.”