The Old Testament often speaks of God as being like a rock to his people. The reference is to the security and safety that God gives to those who trust in him. Just as a high rocky cliff can be a refuge or fortress, so God is a refuge and fortress to his believing people (Genesis 49:24; Psalms 18:2; Psalms 28:1; Psalms 62:2; Psalms 78:35; Isaiah 32:1-2).
A rock is also a solid foundation (Matthew 7:24). This is probably the central idea in Jesus’ statement to the apostles, through their representative Peter, that they were the rock on which he would build his unconquerable church (Matthew 16:18; Ephesians 2:20). (See also CORNERSTONE; STUMBLING BLOCK.)