Cyril of Alexandria, commenting on the book of Haggai, speaks of the Church, the Body of Christ, as the new temple that we must busy ourselves with building and the peace that passes understanding as the reward given to those who build it.
When our Savior came, he appeared as a divine temple, glorious beyond any comparison, far more splendid and excellent than the older temple. He exceeded the old as much as worship in Christ and the gospels exceeds the cult of the laws, as much as truth exceeds its shadows.
Furthermore, I might point out that originally there was just one temple at Jerusalem, in which one people, the Israelites, offered their sacrifices. Since the only-begotten Son became like us, and as Scripture says, though he was Lord and God, he has shone upon us, the rest of the world has been filled with places of worship. Now there are countless worshipers who honor the universal God with spiritual offerings and fragrant sacrifices. This, surely, is what Malachi foretold, speaking, as if in the person of God: I am a great king, says the Lord; my name is honored among the nations, and everywhere there is offered to my name the fragrance of a pure sacrifice.
With justice, therefore, do we say that the final temple, the Church, will be more glorious. To those who are so solicitous for the Church and labor for its construction, Haggai declares that a gift will be made, a gift from heaven given by the Savior. That gift is Christ himself, the peace of all men; through him we have access in the one Spirit to the Father. The prophet goes on to say: I will give peace to this place and peace of soul to save all who lay the foundation to rebuild the temple. Christ too says somewhere: My peace I give you. Paul will teach how profitable this is for those who love: The peace of Christ, he says,which surpasses all understanding will keep your minds and hearts. Isaiah, the seer, made the same prayer: O Lord our God, give us peace, for you have given us everything. Once a man has been found worthy of Christ’s peace, he can easily save his soul and guide his mind to carry out exactingly the demands of virtue.
Haggai, therefore, declares that peace will be given to all who build. One builds the Church either as a teacher of the sacred mysteries, as one set over the house of God, or as one who works for his own good by setting himself forth as a living and spiritual stone in the holy temple, God’s dwelling place in the Spirit. The results of these efforts will profit such men so that each will be able to gain his own salvation without difficulty.
This excerpt from a commentary on Haggai by Saint Cyril of Alexandria (Cap. 14: PG 71, 1047-1050) on the Church as the new temple that must be built and peace for those who build is used in the Roman Office of Readings on the 28th Sunday in Ordinary Time.