Luke 1:2

It is plain that of one kind of knowledge, the end is in the knowledge itself, as in geometry; but of another kind, the end is counted to be in the work, as in medicine; and so it is in the word of God, and therefore having signified the knowledge by the words were themselves eyewitnesses, he points out the work by what follows, and were ministers of the word. It is written in Exodus, The people saw the voice of the Lord. (Exod. 20:18.) Now a voice is rather heard than seen. But it was so written, to show us that men see the voice of the Lord with other eyes, which they only have who are worthy of them. Again in the Gospel, it is not the voice that is perceived, but the Word, which is more excellent than the voice.

(sup.) Luke is a sure witness, because he obtained his knowledge of the truth either from St. Paul's instructions, or the instructions and traditions of the other Apostles, who were themselves eyewitnesses from the beginning.

(Comm. in Act. Apost. Hom. i.) The Evangelist was so far from being content with his single testimony, that he refers the whole to the Apostles, seeking from them a confirmation of his words; and therefore he adds, as they handed them down to us, who were themselves from the beginning eyewitnesses. (sup.) He says, were eyewitnesses, because this is our chief ground for believing in a thing, that we derive it from those who were actually eyewitnesses.

(non occ.) In what he says of the Apostles having been eyewitnesses of the word, he agrees with John, who says, The Word was made flesh, and dwelt among us, and we saw His glory. For the Word by means of the flesh was made visible.

Nevertheless both Matthew and John were obliged in many things that they wrote to consult those who had had means of knowing the infancy, childhood, and genealogy of our Lord, and of seeing the things which he did.