“For who is God, but the Lord? And who is a rock, except our God?—” -Psalm 18:31
Derek Kidner notes that David’s recurrent use of the word rock (ṣûr; cf. verses 2, 46) points to the Song of Moses as part of David’s inspiration for this psalm (see also Deut. 32:4, 31). David’s reflection on his people’s inheritance in Moses should alone encourage Christians since we have an inheritance in both Moses and David, and ultimately in David’s son, Jesus, the Christ.
But even more so, David’s candid and confident declaration, “For who is Elohim, but the YHWH,” points us to the ultimate reality—the source of everything meaningful in life: strength, light, and even help in trouble.