Matthew 28:16-20 At that time the eleven disciples went into Galilee, unto the mountain where Jesus had appointed them. And seeing him they adored: but some doubted. And Jesus coming, spoke to them, saying: All power is given to me in heaven and in earth.
Going therefore, teach ye all nations; baptizing them in the name of the Father, and of the Son, and of the Holy Ghost. Teaching them to observe all things whatsoever I have commanded you: and behold I am with you all days, even to the consummation of the world.
A Homily by St. Jerome the Priest
After his resurrection Jesus was seen on a mountain in Galilee, and there he was worshipped. And, albeit some doubted, their doubts have led to a further establishing of our faith. Then he shewed himself more openly unto Thomas, and pointed out the wound-print of the spear in his side, and the prints of the nails in his hands. And Jesus came and spake unto them, saying: All power is given unto me in heaven and in earth. Yea, all power is given unto him who but a little while before had been crucified, and buried in the grave, and had lain among the dead, but who also had risen again. Power is given unto him in heaven and in earth, that he who of everlasting had been King of heaven, might have a monarchy on earth also, through the faith of them which believe in him. Go ye, therefore, saith he, and teach all nations, baptizing them in the Name of the Father, and of the Son, and of the Holy Ghost. First they were to teach all nations; then they were to wash with water such as had been taught. For it cannot be that the body should receive the Sacrament of Baptism if the mind have not first received the truth of the Faith. And they were to be baptized: In the Name of the Father, and of the Son, and of the Holy Ghost: for, even as the Godhead of the Father, and of the Son, and of the Holy Ghost, is all One, so is the one grace of Baptism the gift of all three divine Persons; and the Name of the Trinity is the Name of one God, not of three. Teaching them to observe all things whatsoever I have commanded you. The order of the Lord's commands to the Apostles is important. First, to teach all nations; secondly, to make them partake in the Sacrament of the Faith; thirdly, when they had believed and been baptized, to teach them what to observe. And lest we should think that he commanded things light and few, he hath said: All things whatsoever I have commanded you : so that all who have believed, and have therefore been baptized in the Name of the Trinity, are bound to observe all things whatsoever he hath commanded. And lo, saith he, I am with you alway, even unto the end of the world. He who promiseth that he will be with his disciples, even unto the end of the world, doth give them thereby to know that they will live for ever, and that he will never fail any which believe in him.