Peter had already described his readers as “living stones” who are “being built up as a spiritual house,” thus included in God’s construction project. Through the last words of the quote from Isaiah 28:16, the apostle qualifies these living stones as “believers” (as he had already done in 1 Peter 1:8). This is the pervasively Biblical thought that one is united to Christ by faith.
6 For it stands in Scripture: “Behold, I am laying in Zion a stone, a cornerstone chosen and precious, and whoever believes in him will not be put to shame.”