Catena Aurea on Matthew 1:22–23: Petrus Alfonsi

For we know not that any man of that day was called Emmanuel. But the Hebrew objects, How can it be that this was said on account of Christ and Mary, when many centuries intervened between Ahaz and Mary? But though the Prophet was speaking to Ahaz, the prophecy was yet not spoken to him only or of his time only; for it is introduced, “Hear, O house of David;” [Isa 7:13] not, ‘Hear, O Ahaz.’

Again, “The Lord Himself shall give you a sign;” meaning He, and none other; from which we may understand that the Lord Himself should be the sign. And that he says “to you,” (plur.) and not ‘to thee,’ shews that this was not spoken to Ahaz, or on his account only.