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But as the engrafted wild olive does not certainly lose the substance of its wood, but changes the quality of its fruit, and receives another name, being now not a wild olive, but a fruit-bearing olive, and is called so; so also, when man is grafted in by faith and receives the Spirit of God, he certainly does not lose the substance of flesh, but changes the quality of the fruit [brought forth, i.e.,] of his works, and receives another name, showing that he has become changed for the better, being now not [mere] flesh and blood, but a spiritual man, and is called such. Then, again, as the wild olive, if it be not grafted in, remains useless to its lord because of its woody quality, and is cut down as a tree bearing no fruit, and cast into the fire; so also man, if he does not receive through faith the engrafting of the Spirit, remains in his old condition, and being [mere] flesh and blood, he cannot inherit the kingdom of God. Rightly therefore does the apostle declare, “Flesh and blood cannot inherit the kingdom of God;” and, “Those who are in the flesh cannot please God:” not repudiating [by these words] the substance of flesh, but showing that into it the Spirit must be infused. And for this reason, he says, “This mortal must put on immortality, and this corruptible must put on incorruption.” And again he declares, “But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you.” He sets this forth still more plainly, where he says, “The body indeed is dead, because of sin; but the Spirit is life, because of righteousness. But if the Spirit of Him who raised up Jesus from the dead dwell in you, He that raised up Christ from the dead shall also quicken your mortal bodies, because of His Spirit dwelling in you.” And again he says, in the Epistle to the Romans, “For if ye live after the flesh, ye shall die.” [Now by these words] he does not prohibit them from living their lives in the flesh, for he was himself in the flesh when he wrote to them; but he cuts away the lusts of the flesh, those which bring death upon a man. And for this reason he says in continuation, “But if ye through the Spirit do mortify the works of the flesh, ye shall live. For whosoever are led by the Spirit of God, these are the sons of God.
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The Church Fathers (The Complete Ante-Nicene & Nicene and Post-Nicene Church Fathers Collection)