39 Faith, hope and charity go together. Hope is practised through the virtue of patience, which continues to do good even in the face of apparent failure, and through the virtue of humility, which accepts God's mystery and trusts him even at times of darkness. Faith tells us that God has given his Son for our sakes and gives us the victorious certainty that it is really true: God is love! It thus transforms our impatience and our doubts into the sure hope that God holds the world in his hands and that, as the dramatic imagery of the end of the Book of Revelation points out, in spite of all darkness he ultimately triumphs in glory. Faith, which sees the love of God revealed in the pierced heart of Jesus on the Cross, gives rise to love. Love is the light—and in the end, the only light—that can always illuminate a world grown dim and give us the courage needed to keep living and working. Love is possible, and we are able to practise it because we are created in the image of God. To experience love and in this way to cause the light of God to enter into the world—this is the invitation I would like to extend with the present Encyclical.
Source: Deus Caritas Est (Vatican.va)