This hymn by Charles Wesley is often sung at Pentecost. It comes from an old testament passage in Leviticus 6:13, “The fire must be kept burning on the altar continuously; it must not go out.” (NIV)

This hymn also refers to John Wesley’s “Aldersgate experience” in 1738, when he received an experience of his heart being warmed by the fire of the Holy Spirit. The celestial fire came from above and kindled a flame in the “altar of my heart.”