Tertullian

By the mouth of Isaiah also [God] has asked concerning him, "Who is there among you that hears God? Let him hear the voice of his Son." When, therefore, he here presents him with the words, "This is my beloved Son," this clause is of course understood, "who I have promised." For if he once promised and afterwards says, "This is he," it is suitable conduct for one who accomplishes his purpose that he should utter his voice in proof of the promise that he had formerly made; but unsuitable in one who is amenable to the retort, "Can you, indeed, have a right to say, 'This is my son,' concerning whom you have given us no previous information, any more than you have favored us with a revelation about your own prior existence?"