The Five Books Against Marcion by Tertullian
Chapter XII.--Isaiah's Prophecy of Emmanuel. Christ Entitled to that Name.
And challenge us first, as is your wont, to consider Isaiah's description of Christ, while you contend that in no point does it suit. For, to begin with, you say that Isaiah's Christ will have to be called Emmanuel; then, that He takes the riches of Damascus and the spoils of Samaria against the king of Assyria. But yet He who is come was neither born under such a name, nor ever engaged in any warlike enterprise. I must, however, remind you that you ought to look into the contexts of the two passages. For there is immediately added the interpretation of Emmanuel, |God with us;| so that you have to consider not merely the name as it is uttered, but also its meaning. The utterance is Hebrew, Emmanuel, of the prophet's own nation; but the meaning of the word, God with us, is by the interpretation made common property. Inquire, then, whether this name, God-with-us, which is Emmanuel, be not often used for the name of Christ, from the fact that Christ has enlightened the world. And I suppose you will not deny it, inasmuch as you do yourself admit that He is called God-with-us, that is, Emmanuel. Else if you are so foolish, that, because with you He gets the designation God-with-us, not Emmanuel, you therefore are unwilling to grant that He is come whose property it is to be called Emmanuel, as if this were not the same name as God-with-us, you will find among the Hebrew Christians, and amongst Marcionites too, that they name Him Emmanuel when they mean Him to be called God-with-us; just indeed as every nation, by whatever word they would express God-with-us, has called Him Emmanuel, completing the sound in its sense. Now since Emmanuel is God-with-us, and God-with-us is Christ, who is in us (for |as many of you as are baptized into Christ, have put on Christ| ), Christ is as properly implied in the meaning of the name, which is God-with-us, as He is in the pronunciation of the name, which is Emmanuel. And thus it is evident that He is now come who was foretold as Emmanuel, because what Emmanuel signifies is come, that is to say, God-with-us.