For since we have received, delivered unto us by God, graces and doctrines which are above man, (as, for example, the rule of a heavenly life, power against evil spirits, the adoption and the knowledge of the Father and the Word, the gift of the Holy Spirit,) our adversary the devil goeth about seeking to steal from us the seed of the word which has been sown. But the Lord, shutting up in us His teaching as His own precious gift, warns us, lest we be deceived. And one very great gift He gives us, the word of God, that not only we be not led away by what appears, but even if there is ought lying concealed, by the grace of God we may discern it. For seeing that the devil is the hateful inventor of evil, what he himself is he conceals, but craftily assumes a name desirable to all; just as if a man wishing to get into his power some children not His own, should in the absence of the parents counterfeit their looks, and lead away the children who were longing for them. In every heresy then the devil says in disguise, “I am Christ, and with me there is truth.” And so it follows, For many shall come in my name, saying, I am Christ; and the time draweth near.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Orat. 1. cont. Arian.