By day the Lord commands his steadfast love, and at night his song is with me, a prayer to the God of my life.” (Psalm 42:8, ESV)

If Ps 42 and 43 were originally one psalm (Ps. 43 is the only Psalm without a title), then Ps. 42.8 stands at the exact center of the two psalms, which is a way that the Hebrews emphasized something.  It was the key to what was written.

“Steadfast love” is “hesed” in the Hebrew.  A word that expresses God’s loyal or covenant love towards his own people.  The Hebrews used it again and again to emphasize God’s love for them. In this case God commands [instructs, orders, tells, gives direction, decrees] his hesed.  He calls it up into useful action in the benefit of his own people.

If God’s hesed is with David in the day, his song is no less with David at night.  In essence David restates what he has just said in another way, this is the parallelism of Hebrew poetry.

His point:  God’s loving care and concern are with David [and therefore with every God worshipper] both day and night.  Spurgeon comments:  “No day shall ever dawn on an heir of grace and find him altogether forsaken of his Lord.” Nor shall any night fall.