7 But what a gnawing worm of the soul is it, what a plague-spot of our thoughts, what a rust of the heart, to be jealous of another, either in respect of his virtue or of his happiness; that is, to hate in him either his own deservings or the divine benefits— to turn the advantages of others into one's own mischief— to be tormented by the prosperity of illustrious men— to make other people's glory one's own penalty, and, as it were, to apply a sort of executioner to one's own breast, to bring the tormentors to one's own thoughts and feelings, that they may tear us with intestine pangs, and may smite the secret recesses of the heart with the hoof of malevolence.
To such, no food is joyous, no drink can be cheerful. They are ever sighing, and groaning, and grieving; and since envy is never put off by the envious, the possessed heart is rent without intermission day and night. Other ills have their limit; and whatever wrong is done, is bounded by the completion of the crime. In the adulterer the offense ceases when the violation is perpetrated; in the case of the robber, the crime is at rest when the homicide is committed; and the possession of the booty puts an end to the rapacity of the thief; and the completed deception places a limit to the wrong of the cheat.
Jealousy has no limit; it is an evil continually enduring, and a sin without end. In proportion as he who is envied has the advantage of a greater success, in that proportion the envious man burns with the fires of jealousy to an increased heat.
Source: The Treatises of Cyprian (New Advent)