"the Source of life that makes us holy ... you must be holy"

"the Holy Spirit, the Spirit of the love of the Father and of the Son, is the Source of life that makes us holy, “because God's love has been poured into our hearts through the Holy Spirit which has been given to us” (Rom 5:5). Nevertheless, it is not enough to know the Spirit; we must welcome Him as the guide of our souls, as the “Teacher of the interior life” who introduces us to the Mystery of the Trinity, because He alone can open us up to faith and allow us to live it each day to the full. The Spirit impels us forward towards others, enkindles in us the fire of love, makes us missionaries of God’s charity."

"you must be holy and you must be missionaries since we can never separate holiness from mission"

http://www.vatican.va/holy_father/benedict_xvi/messages/youth/documents/hf_ben-xvi_mes_20070720_youth_en.html

Hat tip to http://www.armybarmy.com/blog.html whose source was http://theworldforgod.blogspot.com/2008/07/part-of-world-youth-day-celebrations.html