From the “spiritual milk” of the Word of God that nourishes the community of newborns, the disciple progresses to another image rich in biblical significance: the stone, which can be the ‘cornerstone’ (cf. Is 28:16) that the believer relies on in faith, or the ‘keystone’ (cf. Ps 118:22), which serves as the key and capstone of the building (cf. Zec 4:7). The development and application of this image form the core of the letter and one of the most beautiful teachings of the New Testament on the Christian community.