Acts 4:11

Peter showed that this teaching did not lead the people away from God but rather fulfilled something that God had predicted. In quoting Psalms 118:22 Peter applied to Jesus Christ what David had said about the nation Israel (cf. Matthew 21:42; Mark 12:10; Luke 20:17). Israel’s leaders had rejected Jesus as an unacceptable Messiah, but He would prove to be the most important part of what God was building.

Some scholars believe Peter meant that Jesus was the cornerstone, the foundation of what God was building (cf. Isaiah 28:16; 1 Peter 2:7). Others believe he meant the capstone, the final piece of what God was building (cf. Daniel 2:34-35). [Note: E.g., Longenecker, pp. 304-5.] If the former interpretation is correct, Peter was probably anticipating the church as a new creation of God (cf. 1 Peter 2:4-8). In the latter view, he was viewing the Messiah as the long-expected completion of the house of David. Since Peter was addressing Israel’s rulers, I think he probably meant that Jesus was the capstone, their Messiah. These rulers, the builders of Israel, had rejected their Messiah.