2 However, there is a difficulty in deciding as regards this verse too, whether the words were really spoken to Christ, for there is a discrepancy in the narratives. For while two evangelists, Matthew and Luke, both alike tell of the centurion whose servant was sick, and to whom these words of Jesus are supposed to have applied, that He had not seen so great faith, no, not in Israel, as in this man, though a Gentile and a Pagan, because he said that he was not worthy that Jesus should come under his roof, but wished Him only to speak the word, and his servant should be healed; Matthew alone adds that Jesus went on to say, "Verily I say unto you, that many shall come from the east and from the west, and shall sit down with Abraham, and Isaac, and Jacob, in the kingdom of heaven; but the children of the kingdom shall be cast into outer darkness."
By the many who should come are meant the Pagans, on account of the centurion, in whom, although he was a Gentile, so great faith was found; and the children of the kingdom are the Jews, in whom there was no faith found. Luke, again, though he too mentions the occurrence in his Gospel as part of the narrative of the miracles of Christ, says nothing of Abraham, Isaac, and Jacob. If it is said that he omitted it because it had been already said by Matthew, why does he tell the story at all of the centurion and his servant, since that, too, has the advantage of being recorded at length in Matthew's ingenious narrative?
But the passage is corrupt. For, in describing the centurion's application to Jesus, Matthew says that he came himself to ask for a cure; while Luke says he did not, but sent elders of the Jews, and that they, in case Jesus should despise the centurion as a Gentile (for they will have Jesus to be a thorough Jew), set about persuading Him, by saying that he was worthy for whom He should do this, because he loved their nation, and had built them a synagogue; here again taking for granted that the Son of God was concerned in a pagan centurion having thought it proper to build a synagogue for the Jews.
The words in question are, indeed, found in Luke also, perhaps because on reflection he thought they might be genuine; but they are found in another place, and in a connection altogether different. The passage is where Jesus says to His disciples, "Strive to enter in at the strait gate; for many shall come seeking to enter in, and shall not be able. When once the Master of the house has entered in, and has shut to the door, you shall begin to stand without, and to knock, saying Lord, open to us.
And He shall answer and say, I know you not. Then you shall begin to say, We have eaten and drunk in Your presence, and You have taught in our streets and synagogues; but He shall say unto you, I know not whence you are; depart from me, all you workers of iniquity. There shall be weeping and gnashing of teeth, when you shall see Abraham, and Isaac, and Jacob, and all the prophets, entering into the kingdom of God, and you yourselves cast out. And they shall come from the east, and from the west, and from the north, and from the south, and shall sit down in the kingdom of God." The part where it is said that many shall be shut out of the kingdom of God, who have only borne the name of Christ, without doing His works, is not left out by Matthew; but he makes no mention here of Abraham, and Isaac, and Jacob.
In the same way, Luke mentions the centurion and his servant, without alluding in that connection to Abraham, and Isaac, and Jacob. Since it is uncertain when the words were spoken, we are at liberty to doubt whether they were spoken at all.
Source: Reply to Faustus the Manichaean (New Advent)