Charity and freedom are inseparable. Love must be free. Only charity is perfectly free. Love is loved for itself, not determined by anything else outside itself.
It is not drawn by the satisfaction of anything less than itself. Only in charity, that is disinterested love, is love perfectly spontaneous.
All love that is less than charity ends in something less than itself. Perfect charity is its own end, and is therefore free, not determined by anything else. God alone is perfectly free, infinitely free. He is Love Loving Himself. Because He is absolutely free, His love can do whatever it likes.
We are constituted in His image by our freedom— which is not absolute, but contingent. That is, we are free in proportion as we share His freedom, which is absolute. We are free in the sense that no one determines our free choices: we are so much our own masters that we can even resist God, as we know to our sorrow! But we are also free to love for the sake of loving, to love God because He is Love, and to find ourselves in the perfect freedom of Love’s own giving of itself.