My friends, once again: what does it mean to build on the rock? Building on the rock also means to build on Peter and with Peter. In fact the Lord said to him: "You are Peter, and on this rock I will build my Church, and the powers of death shall not prevail against it" (Mt 16:18). If Christ, the Rock, the living and precious stone, calls his Apostle "rock", it means that he wants Peter, and together with him the entire Church, to be a visible sign of the one Saviour and Lord. Here, in Kraków, the beloved city of my Predecessor John Paul II, no one is astonished by the words "to build with Peter and on Peter". For this reason I say to you: do not be afraid to build your life on the Church and with the Church. You are all proud of the love you have for Peter and for the Church entrusted to him. Do not be fooled by those who want to play Christ against the Church. There is one foundation on which it is worthwhile to build a house. This foundation is Christ. There is only one rock on which it is worthwhile to place everything. This rock is the one to whom Christ said: "You are Peter, and on this rock I will build my Church" (Mt 16:18). Young people, you know well the Rock of our times. Accordingly, do not forget that neither that Peter who is watching our gathering from the window of God the Father, nor this Peter who is now standing in front of you, nor any successive Peter will ever be opposed to you or the building of a lasting house on the rock. Indeed, he will offer his heart and his hands to help you construct a life on Christ and with Christ.