Charles Ellicott Commentary Psalms 42:8

"[Yet] Jehovah will command his lovingkindness in the day-time; And in the night his song shall be with me, [Even] a prayer unto the God of my life." — Psalms 42:8 (ASV)

Yet the Lord. —Better, By day Jehovah shall command (or, literally, Jehovah command) his grace.

And in the night his song — that is, a song to Him; but the emendation shîrah, “song,” for shîrôh, “his song,” commends itself. The parallelism of this verse seems to confirm the conclusion drawn from the sentence at end of Book II., that the title “prayer,” and “song” were used indiscriminately for any of the hymns in religious use.