The eleven disciples mentioned here are the eleven apostles chosen by the Lord Jesus (chapter 10:2-4, Acts 1:13), to whom he had appeared when they met on the day of His resurrection, and the next Sunday in Jerusalem after completion of the Feast of Unleavened Bread. He had told them to go to Galilee, and so they did.
John tells us that seven disciples were fishing on the Sea of Tiberias at night without success, but when they returned at dawn the Lord stood before them for the third time, at the beach, and provided them with an abundant catch, then offered them a meal of bread and fish. Then the Lord told Peter to tend and feed His flock (John 21: 1-24). See also HERE
Matthew now relates what happened during the other times He was with them in Galilee, and we find other reports in Mark 16:15-18 and 1 Corinthians 15:6 which probably refer to the same occasion. Joining the three, we learn that the disciples had gone into a mountain in Galilee, following instructions of the Lord, and found Him there.
It is likely that there were not only the apostles, but a large crowd, over five hundred people, followed these as we read in the letter to the Corinthians. Seeing Him, they worshipped Him, acknowledging His Divine Person and giving Him the reverence and honour due. However, some doubted. It was a sublime scene, where the risen Christ, without any apparatus or visible demonstration of military might and majesty said to them all: “All authority has been given me in heaven and in earth."
What a startling statement of their Master! It was as if He were already in heaven, having dominion over all, and the legions of angels ready to do whatever He ordained. How would the leaders of the people, and the mighty Caesar, receive Him? How would He enforce such authority He claimed to have?
As at other times, the Lord Jesus presented Himself as a normal person, without some supernatural feature about Him to distinguish Him from others. That was how the disciples knew Him, because they lived with Him doing their daily tasks. He had manifested Himself as a brilliant and wise teacher with an unblemished character, but was woefully rejected by the priests and teachers in the temple, and crucified as a malefactor just a few days ago!
No one had seen Him in the act of rising from the dead, as they had seen Lazarus and others; however, the evidence that convinced them was that His body disappeared from the tomb leaving its wrappings untouched, despite heavy Roman guard. Furthermore, He was again before them, in perfect health and of course very much alive. One of those who had doubted, Thomas, said after the evidence he witnessed: "My Lord and my God” (John 20:28).
Still, the news that He had received all authority in heaven and on earth was almost unbelievable! His previous authority or power over demons or diseases, over nature and even over death had been shown (chapters 7:29, 11:27, 21:23 etc.) and ought to be sufficient to persuade those who doubted that He was indeed the Messiah, the Son of God.
However, to have been given all authority in heaven and on earth was another dimension altogether. It is no wonder that, of this group of more than five hundred disciples gathered on the mountain, men and women, some doubted. As even the closest disciples who had had difficulty at first in accepting the reality of His resurrection, they were not easily persuaded.
Having informed His disciples of the authority that He now had, the Lord Jesus continued by giving them what is called "The Great Commission" based and sustained by that authority and with which He promises to always be present with His people.
The Lord Jesus told His disciples they were to do three things:
Raise disciples of all nations. In other words, to publicly proclaim the Gospel throughout the world, and to teach those who were willing to listen, to clearly know the doctrines of Christ.
To baptize disciples in the name of the Father and of the Son and of the Holy Spirit. We clearly have here the divine trinity with its three persons, each different from the others but all having divine attributes individually, all three being one God. However, Christian baptism is done in the name of the three individually, thus leaving no doubt that God is at work in all three.
Teaching them to observe all the things the Lord commanded. Evangelization is not to just preach the Gospel, enlighten those who are interested and baptize those who are saved by faith in the Lord Jesus Christ. The Lord knew that His flock would be growing through the centuries, and the disciples who had already received His teachings needed to prepare others to expand and continue the work of the Lord. This is how Christ's church grows through the world and along the centuries until His return.
Just one person does not necessarily exercise all these tasks. Early on in the church, we read that the Holy Spirit gave it evangelists, pastors and teachers better to serve each of these sectors.
Mark tells us that the Lord gave a list of things that would accompany those who believed in what He was saying. He said this because He knew that some doubted.
The believers “In My name they will cast out demons; they will speak with new tongues; they will take up serpents; and if they drink anything deadly, it will by no means hurt them; they will lay hands on the sick, and they will recover." (Mark 16:17, 18). It is understood that the Lord was considering those who believed as a group, and some of them would make these signs, not each one of them. In the book of Acts, we see the fulfilment of some of these signs.
This commission receives the assurance of the Lord Jesus: "and lo, I am with you always, even to the end of the age." He, the Everlasting Father, made this promise binding, essential for the maintenance and growth of His church on earth. True disciples of the Lord Jesus can count on His support to obey his Commission, until "the end of the age.”
When will the end of the age be, only God knows. This is not a century of one hundred years, but a period of time in which we still are, during which there will be chance of salvation for every sinner.
Here ends the Gospel of Matthew.
Addendum:
The Lord appeared to His disciples over a period of forty days after His resurrection. Luke gives us more information about the final days before the ascension of Jesus Christ, both in his Gospel and in Acts:
Christ told His disciples to return to Jerusalem, appeared to them again there, and instructed them to stay in that city until they received the gift of the Holy Spirit. He led them to Bethany, and lifting His hands blessed them.
“Now it came to pass, while He blessed them, that He was parted from them and carried up into heaven. The disciples worshipped Him and returned to Jerusalem with great joy, and were continually in the temple praising and blessing God. Amen" (Luke 24: 51-53).
16 Then the eleven disciples went away into Galilee, to the mountain which Jesus had appointed for them.
17 When they saw Him, they worshipped Him; but some doubted.
18 And Jesus came and spoke to them, saying, "All authority has been given to Me in heaven and on earth.
19 Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit,
20 teaching them to observe all things that I have commanded you; and lo, I am with you always, even to the end of the age." Amen.
Matthew 28, verses 16 to 20