5 Therefore did the Lord also say to His disciples after the resurrection, “O thoughtless ones, and slow of heart to believe all that the prophets have spoken! Ought not Christ to have suffered these things, and to enter into His glory?” And again does He say to them: “These are the words which I spoke unto you while I was yet with you, that all things must be fulfilled which were written in the law of Moses, and in the prophets, and in the Psalms, concerning Me. Then opened He their understanding, that they should understand the Scriptures, and said unto them, Thus it is written, and thus it behooved Christ to suffer, and to rise again from the dead, and that repentance for the remission of sins be preached in His name among all nations.” Now this is He who was born of Mary; for He says: “The Son of man must suffer many things, and be rejected, and crucified, and on the third day rise again.” The Gospel, therefore, knew no other son of man but Him who was of Mary, who also suffered; and no Christ who flew away from Jesus before the passion; but Him who was born it knew as Jesus Christ the Son of God, and that this same suffered and rose again, as John, the disciple of the Lord, verifies, saying: “But these are written, that you might believe that Jesus is the Christ, the Son of God, and that believing you might have eternal life in His name,” — foreseeing these blasphemous systems which divide the Lord, as far as lies in their power, saying that He was formed of two different substances. For this reason also he has thus testified to us in his Epistle: “Little children, it is the last time; and as you have heard that Antichrist does come, now have many antichrists appeared; whereby we know that it is the last time. They went out from us, but they were not of us; for if they had been of us, they would have continued with us: but [they departed], that they might be made manifest that they are not of us. Know therefore, that every lie is from without, and is not of the truth. Who is a liar, but he that denies that Jesus is the Christ? This is Antichrist.”
Source: Adversus haereses (New Advent)