Rocks and stones have long been valued as building materials because of their stability and strength. A structure made of wood can burn to the ground, but buildings and monuments made entirely of stone endure for centuries. They stay ever the same even as everything else changes around them.
Of course, we know that even stone changes over time through erosion and other processes. Still, this change is so slow and imperceptible that, to our everyday experience, it is as if rocks and stones never change. Consequently, Scripture is fond of likening God to a rock in order to convey His immutability — His inability to change in His essential nature. This is the point of today’s passage.
Moses speaks of the Rock, referring to the perfections of the Lord (Deut. 32:4). “All his ways are justice,” for it is impossible for Him not to be holy. He never does evil but must, as Abraham implies in His dialogue with God, always do what is right (Gen. 18:25). Our character and personality traits may change, leading us to do things that are not in keeping with how we have behaved in the past, but the Lord is unchanging in His character.
A rock can also serve as the foundation for a structure, and so our Creator serves as the ultimate foundation for all integrity and justice. He is just and upright (Deut. 32:4); His law reflects His very being and is therefore able to serve as the basis for all of life. God has revealed His perfect law to His people (Ps. 19:7), one that can be applied to every situation we will ever face through the illumination of His Holy Spirit. We never need wonder whether His laws are just, even as we know that the laws of humanity are imperfect and incapable of providing a final, secure foundation for all of life. Matthew Henry writes, “God is the rock, for he is in himself unchangeable, immovable, and he is to all that seek him and run to him an impenetrable shelter, and to all who trust in him an everlasting foundation.”
The firmness of a rock also makes it a good metaphor for our faithful God of promise (Deut. 32:4). Human promises can be made and broken in an instant, but the Lord never fails to keep a commitment that He has made. We routinely break our covenants with one another, but our Father never breaks His covenant with us (Lev. 26:44).
At the end of the Sermon on the Mount, Jesus offers us only two options. Either we will build our lives on His teaching and survive in that last day or we will build our lives on the sinking sand of men’s opinions and be washed away into eternal destruction (Matt. 7:24–27). Because this sermon is a part of God’s living Word, Jesus presents the same choice to us today. Will we continue to walk in His ways?