The Lord Our Rock
Psalm 18:46 (ESV) … “The Lord lives, and blessed be my rock, and exalted be the God of my salvation—”
More than twenty years ago the great professor of classics at Auckland University, E. M. Blaiklock, wrote a series of articles for Eternity entitled “New Light on Bible Imagery.”
One of the images he wrote about was rock. He showed that it has several uses.
First, it is an image for protection and shade. In the hot, sandy lands of the Bible the struggle of life against the merciless elements is intense in a way we can hardly appreciate in our more temperate climes. When the spring rains come a light carpet of green, doomed to be scorched by the sun and then covered with sand in just a few short weeks, will emerge on the desert’s edge. But set a rock in the sand, and soon a small oasis develops on the boulder’s leeward side. The desert’s feeble life prospers under the rock’s protection. Similarly, a man traveling through the desert during the hottest hours of the day can find shade in the rock’s shadow and can survive and continue his journey. These ideas are present in verses like Isaiah 32:2, which describes the king as “the shadow of a great rock in a thirsty land.” Protected by a righteous king, many weaker people may prosper. Yet the king is himself sheltered by God, as David confesses in Psalm 18. It is because the Lord was his rock that David thrived.
The second use of this image is to portray God as a refuge for his people. This idea is prominent in Psalm 18, because David is thinking of God’s protection during the years he was forced to hide from Saul and later Absalom. David knew every cranny, crack, and secret hiding place in the vast, rocky wilderness. So when he fled to the rocks, he knew that he would be safe in their protection. From the height of some great rock David could look down into the canyon below and watch as his enemies pursued him hopelessly.
The vision of David perched on some high rock suggests the third biblical use of this image: having a sure foundation beneath one’s feet. Here a rock is contrasted with mire and sand, as in Psalm 40:2: He [the Lord] lifted me out of the slimy pit, out of the mud and mire; he set my feet on a rock and gave me a firm place to stand.
Jesus used this image in the closing lines of the Sermon on the Mount, in which he contrasted the person who builds his life on sand with the person who builds on rock. The person who builds on sand suffers the loss of everything when the rains come. His house is swept away. The house that is built on rock stands firm against the rains, flood, wind, and storm “because it had its foundation on the rock” (Matt. 7:25).
Psalm 18 is one long testimony to the faithfulness of God in each of these aspects. He is a shelter, a stronghold, and a firm foundation for all who build on him.
 Boice, J. M. (2005). Psalms 1–41: An Expositional Commentary (pp. 147–148). Grand Rapids, MI: Baker Books.