When the chief priests and scribes and elders rejected Jesus and his ministry, Jesus quoted Psalm 118:22 to them in relation to himself (Mark 12:10), thereby indicating that he was the fulfillment of the psalmist’s words. Peter was undoubtedly a witness to that discussion and understood that Jesus was in fact the fulfillment of the “cornerstone” reference (Acts 4:10–11). By quoting Psalm 118:22 in the present context, Peter is building on the Lord’s own use of that Old Testament passage.
7 So the honor is for you who believe, but for those who do not believe, “The stone that the builders rejected has become the cornerstone,”