In the ancient world, before the explosives and powerful tools we have today, rocks were impervious, seemingly eternal, and solid. In times of danger, a cliff formed a secure foundation or a safe hiding place, as David found when he was a fugitive being chased
by Saul (2 Sam 22:2-4, 32). The physical safety offered by rocks made them a fitting image for the security offered by God: “He alone is my rock and my savior-my stronghold. I cannot be severely shaken” (Ps 62:2; see also 31:2-3; 62:6-7). God is the solid foundation upon which a believer builds his or her life.
STONE OF STUMBLING
A rock or a stone can also be an obstacle that causes one to stumble or gets in the way. God is a rock in this sense of the term as well, for “the LORD of Armies is holy. . . .He will be a place of safety for you. But he will be a rock that makes people trip and a stumbling block for both kingdoms of Israel” (Isa 8:13-14; cf. Dan 2:34; Rom 9:32-33). Those who wish to earn their salvation through adherence to the law will stumble over the Messiah who offers salvation freely to those who come to him to be saved (Rom 11:9, 11-12; 1 Cor 1:23). On the other hand, those who take refuge in Christ and claim him as their Rock will not stumble (Ps 91:12).
IMAGES OF LIFELESSNESS
The lifelessness and hardness of stones makes them a fitting symbol for people who are spiritually dead. Ezekiel prophesied that God will remove the hearts of stone from his people and replace them with hearts flesh-a picture of an unresponsive, hard, nonliving thing being replaced with something that is responsive and alive (36:26 NIV). Paul picked up this image in 2 Corinthians 3:3 as he contrasted the dead law, written on stone, with living letters written on people’s hearts. The Christian life is one of spirit-filled warmth and action, not one of dead works. Jesus used as an image of lifelessness when he told the Pharisees that if the disciples were quite, the rocks would cry out (Luke 19:40). Even the nonliving parts of creation will praise God if people are so spiritually blinded that they don’t praise him, because he is worthy of all praise.
LIVING STONES
The solid timelessness of stone makes it an appropriate symbol for the eternal kingdom of God. Other kingdoms will come and go, but God’s kingdom is eternal, just as a stone is more permanent than Nebuchadnezzar’s statue made by human hands (Dan 2:34-44). The temporary manifestation of the kingdom of God, the universal church, is built on a rock as well. In the short term, the image of the apostle Peter (or perhaps his simple declaration of Christ’s identity) represents the foundation God would use to build his church that would stand firm through the ages (Matt 16:13-20). But in an eternal sense, Peter builds on this imagery further by saying that all believers are living stones built into a spiritual temple. We were once spiritually dead like a stone but have been given a heart of flesh through Christ and are now living stones. In this metaphor Christ himself is, of course, the cornerstone, the one who is the most important stone, the first one laid, and who holds the building up (Isa 28:16; Acts 4:11; Eph 2:2-21; 1 Pet 2:4-8). The rock of refuge and safety of the Old Testament has become the chief cornerstone in the New Testament.
Source: The A To Z guide to Bible Signs & Symbols (Understanding Their Meaning and Significane) Stone/Rock pg 230 & 231