The story in Numbers 20 of Moses striking the rock (when he was commanded to speak to it) is familiar to us. In your mind, what size was the rock? We may think of something small when we think “rock,” but remember that it gave enough water for all the Israelites (a couple million people). By definition, the rock that Moses struck was a large, cliff-like, mountainous mass.
The same Hebrew word, sela, is used repeatedly in the Old Testament as a metaphor for God Himself. Think about these verses: “The Lord is my Rock…Blessed be my Rock…To you I will cry, O Lord my Rock…Be my Rock of refuge…He only is my Rock…the Rock of my strength… my God the Rock of my refuge” (Psa. 18:2, 46; 28:1; 31:2; 62:2, 7; 94:22; etc.).
There isn’t “any Rock like our God” (1 Sam. 2:2). “Even our enemies themselves being judges” know that “their rock is not like our Rock” (Deut. 32:31). Our God is that cliff-like, fortified, mountainous Rock who protects us and in whom we can put our every trust.