8 [16-20] This climactic scene has been called a "proleptic parousia," for it gives a foretaste of the final glorious coming of the Son of Man (Matthew 26:64). Then his triumph will be manifest to all; now it is revealed only to the disciples, who are commissioned to announce it to all nations and bring them to belief in Jesus and obedience to his commandments.
9 [16] The eleven: the number recalls the tragic defection of Judas Iscariot. To the mountain . . . ordered them: since the message to the disciples was simply that they were to go to Galilee (Matthew 28:10), some think that the mountain comes from a tradition of the message known to Matthew and alluded to here. For the significance of the mountain, see the note on Matthew 17:1.
10 [17] But they doubted: the Greek can also be translated, "but some doubted." The verb occurs elsewhere in the New Testament only in Matthew 14:31 where it is associated with Peter's being of "little faith." For the meaning of that designation, see the note on Matthew 6:30.
11 [18] All power . . . me: the Greek word here translated power is the same as that found in the LXX translation of Daniel 7:13-14 where one "like a son of man" is given power and an everlasting kingdom by God. The risen Jesus here claims universal power, i.e., in heaven and on earth.
12 [19] Therefore: since universal power belongs to the risen Jesus (Matthew 28:18), he gives the eleven a mission that is universal. They are to make disciples of all nations. While all nations is understood by some scholars as referring only to all Gentiles, it is probable that it included the Jews as well. Baptizing them: baptism is the means of entrance into the community of the risen one, the Church. In the name of the Father . . . holy Spirit: this is perhaps the clearest expression in the New Testament of trinitarian belief. It may have been the baptismal formula of Matthew's church, but primarily it designates the effect of baptism, the union of the one baptized with the Father, Son, and holy Spirit.
13 [20] All that I have commanded you: the moral teaching found in this gospel, preeminently that of the Sermon on the Mount (Matthew 5-7). The commandments of Jesus are the standard of Christian conduct, not the Mosaic law as such, even though some of the Mosaic commandments have now been invested with the authority of Jesus. Behold, I am with you always: the promise of Jesus' real though invisible presence echoes the name Emmanuel given to him in the infancy narrative; see the note on Matthew 1:23. End of the age: see the notes on Matthew 13:39 and Matthew 24:3.
But Jesus is NOT with us always...Jesus is seated in Heaven alongside the Father...
However, the Holy Spirit is with us always...Jesus says we are filled with the Holy Spirit...And yet Jesus says we are in Him and He is in us...
One doesn't have to go too far down this road to realize that Jesus is speaking of the Trinity...
Jesus sent the Holy Spirit to take His place since Jesus would be gone, but then Jesus says He is here with us...
We don't need to understand it...No one understands it...Just believe it...