Finally, by a high paradox, God enables men to have a Gift-love towards Himself. There is of course a sense in which no one can give to God anything which is not already His; and if it is already His what have you given? But since it is only too obvious that we can withhold ourselves, our wills and hearts, from God, we can, in that sense, also give them. What is His by right and would not exist for a moment if it ceased to be His (as the song is the singer’s), He has nevertheless made ours in such a way that we can freely offer it back to Him. “Our wills are ours to make them Thine.”
C.S. Lewis, The Four Loves (1960; Harcourt Brace: 1991) 128-129.