This setting of Psalm 27:1-6 expresses great confidence in God's protection of his people, a confidence that leads the psalmist to bring “Joyful offerings” (st. 4) to the LORD. The first stanza (originally “Jehovah is my light”) was first published in The Book of Psalms (1871), a text-only psalter that was later published with music in 1887. Stanzas 2-4 (altered) are from the 1912 Psalter, which in turn had altered the 1871 text.
Bert Polman, Psalter Hymnal Handbook
The Christology of the song, “O LORD, You Are My Light” is carefully based on the content of the Apostles’ Creed, and the firmness of the convictions here echo the words of Belgic Confession, Article 20, that God gave “his Son to die, by a most perfect love, and [raised] him to life for our justification, in order that by him we might have immortality and eternal life.” “When [his] benefits are made ours, they are more than enough to absolve us of our sins…(Additionally,) the Holy Spirit kindles in our hearts a true faith that embraces Jesus Christ, with all his merits, and makes him its own, and no longer looks for anything apart from him” (Belgic Confession, Article 22).