In Christian theology, Charity (Latin Caritas) is considered one of the seven virtues and is understood by Thomas Aquinas as "the friendship of man for God", which "unites us to God". He holds it as "the most excellent of the virtues". Further, Aquinas holds that "the habit of charity extends not only to the love of God, but also to the love of our neighbor".
The phrase Deus caritas est from 1 John 4:8--or ? (Theos agap? estin) in the original Greek is translated in the King James Version as: "God is love", and in the Douay-Rheims bible as: "God is charity" (1 John 4:8). Thomas Aquinas does not simply equate charity with "love", which he holds as a passion, not a virtue. The King James Version uses both the words charity and love to translate the idea of caritas/ (agap?): sometimes it uses one, then sometimes the other, for the same concept. Most other English translations, both before and since, do not; instead, throughout they use the same more direct English word love. Love can have other meanings in English, but as used in the New Testament it almost always refers to the virtue of caritas.
Many times when charity is mentioned in English-language bibles, it refers to "love of God", which is a spiritual love that is extended from God to man and then reflected by man, who is made in the image of God, back to God. God gives man the power to act as God acts (God is love), man then reflects God's power in his own human actions towards others. One example of this movement is "charity shall cover the multitude of sins" (1 Peter 4:8). "The practice of charity brings us to act toward ourselves and others out of love alone, precisely because each person has the dignity of a beloved child of God."
Charity is held to be the ultimate perfection of the human spirit, because it is said to both glorify and reflect the nature of God. Confusion can arise from the multiple meanings of the English word "love". As other theological virtues, Charity is divinely infused into the soul; it resides in the will. According to Aquinas, charity is an absolute requirement for happiness, which he holds as man's last goal.
Charity has two parts: love of God and love of man, which includes both love of one's neighbor and one's self.
Though I speak with the tongues of men and of angels, and have not charity, I am become as sounding brass, or a tinkling cymbal. And though I have the gift of prophecy, and understand all mysteries, and all knowledge; and though I have all faith, so that I could remove mountains, and have not charity, I am nothing. And though I bestow all my goods to feed the poor, and though I give my body to be burned, and have not charity, it profiteth me nothing. Charity never faileth: but whether there be prophecies, they shall fail; whether there be tongues, they shall cease; whether there be knowledge, it shall vanish away. For we know in part, and we prophesy in part. But when that which is perfect is come, then that which is in part shall be done away....And now abideth faith, hope, charity, these three; but the greatest of these is charity.
The fruits of charity are joy, peace, and mercy.