All Christian love has its source and exemplar in the love of God. ‘Beloved,’ wrote St. John, ‘if God so loved us, we also ought to love one another’, or again, ‘God is love, and he who abides in love abides in God, and God abides in him.’ St. Paul was equally clear; it is God's love which ‘has been poured into our hearts through the Holy Spirit which has been given to us’, and it is the love of Christ (which is, of course, the love of God revealed in Christ) that constrains us to live no longer for ourselves—the usual way in which our human love is evidenced. Dietrich Bonhoeffer echoed this from his German prison, ‘No one knows what love is except in the self-revelation of God… It is only the concrete action and suffering of Jesus Christ which will make it possible to understand what love is.’ So we must begin with the love of God; and yet our understanding of God's love comes to us through the experience of human love. It was with a picture of an earthly father, surrounded by the human things of home and field, calves and kids, robes and rings, sons and servants, that Jesus made His most vivid portrait of the love of God; and it was not only in dying on Calvary, but also in living in human fellowship with Peter and John, Martha and Mary that Jesus Himself exhibited the Father's love to men.