Origen's Commentary on the Gospel of Matthew

Moreover in regard to the saying, “Let him deny himself,” the following saying of Paul who denied himself seems appropriate, “Yet I live, and yet no longer I but Christ liveth in me;” for the expression, “I live, yet no longer I,” was the voice of one denying himself, as of one who had laid aside his own life and taken on himself the Christ, in order that He might live in him as Righteousness, and as Wisdom, and as Sanctification, and as our Peace, and as the Power of God, who worketh all things in him. But further also, attend to this, that while there are many forms of dying, the Son of God was crucified, being hanged on a tree, in order that all who die unto sin may die to it, in no other way than by the way of the cross. Wherefore they will say, “I have been crucified with Christ,” and, “Far be it from me to glory save in the cross of the Lord, through which the world has been crucified unto me and I unto the world.” For perhaps also each of those who have been crucified with Christ puts off from himself the principalities and the powers, and makes a show of them and triumphs over them in the cross; or rather, Christ does these things in them.