The Lord Jesus Christ and His Apostles
The Lord left his apostles with instructions and with great gifts. The instructions are listed in several distinct places, but the the gifts are more scattered, both in the four gospels and in the book of Acts later, being given as the apostles needed them.
First, about the apostles... just to clarify, here I'm referring to "the disciples" as including anyone who has followed along to hear the Lord, and "the apostles" to mean the twelve men that the Lord recruited specifically, as listed in Matthew 10, Mark 3, and Luke 6.
Who were the apostles? From the lists in Matthew and Mark, which are the same, we have: Simon (Peter), James and John the sons of Zebedee, Andrew (Peter’s brother), Philip, Bartholomew, Matthew (the publican), Thomas, James the son of Alpheus, (as is Matthew, so they are brothers, too), Thaddeus, (also known as Libbeus), Simon the Canaanite (also called Simon the Zealot), and Judas Iscariot. Bartholomew is almost undoubtedly another name for Nathaniel, see John 1. The list in Luke includes another Judas, "Judas the brother of James" and doesn’t have Thaddeus.
The stories of how they were individually chosen differ, especially in the gospel of John, but that these twelve were appointed by the Lord is clear. A point of interest is that - other than Simon the Canaanite and Judas Iscariot they are all from towns around the sea of Galilee - and perhaps those two are as well. These twelve have their names inscribed on the twelve foundations of the walls of the holy city New Jerusalem, in Revelation 21:14 in which there are also the twelve gates. These men were chosen to represent all the different states of the natural human being that can be receptive of the Lord. They are from Galilee because Galilee represents that natural state of the human mind. The number twelve in the Word represents all possible states of mankind.
What is indicated here is that all people, everywhere, can be saved or regenerated if they repent and turn to the Lord in their lives. No one is "outside" of His reach. We are born natural, everyone is, but we are so formed that our minds can be raised to what is higher, called spiritual for our conceptions of Divine truth, or Celestial for our perceptions of Divine good. But we all start in a natural state and can only move upward by listening to the Lord’s teachings in His Word, and following Him as those Apostles did.
Not all of our natural states are states of good; they can be selfish, domineering, and cruel. But the Lord said that He came "not to save the just but to call sinners to repentance". Perhaps this is why Simon the Canaanite and Judas were two that He called. Simon is little known, but in some places in the Word, "Canaan signifies an external worship without a true internal worship". (See Arcana Coelestia 1060). Can the Lord work with that - with external worship that's internally barren? Yes, as a starting point. And, even Judas, who betrayed the Lord so terribly, we are told, repented of his betrayal of the Lord. (Matthew 27:3-5)
The Lord's Instructions to the Apostles
The two most comprehensive sets of instructions are in Luke 10:1-17 where seventy Disciples are sent out two by two, apparently to a specified list of cities that Jesus intends to visit, and then in Matthew 20:1-19 where the chosen twelve Apostles are sent out to all Israel. Later, as recorded in different epistles, the Apostles go out further, through a wide region.
The basic instructions were to preach that the kingdom of heaven is near, that all should be led to repent of their sins, and that all who wish should be baptized in the name of the Father and the Son and of the Holy Spirit. The Apostles should not take any money or extra clothing along, and they were to depend entirely on the Lord’s providence with no doubt that they shall be welcomed, fed, and sheltered. If they were welcomed, they should stay and preach the good news about the risen Lord and His teachings, and if they were not, they should shake from their feet the dust of that place and go on to a place where they were welcome. See Matthew 10, 28, Mark 13, 16, Luke 9, 10:24.
There are several assurances for the twelve. The Lord has told them to stay in Jerusalem until the Holy Spirit is sent to strengthen them, and in John 20 where the ten are gathered it is said that He breathed on them and said, "Receive ye the Holy Spirit". Also, in his long talk with them in John 14, 15, 16) He assures them that his crucifixion and death are necessary to his mission and they should even rejoice that it is coming. He shows them from scripture that it has all been prophesied from long ago, (see Mark 4:34) and that what seems to them a tragedy, is truly His glorification and the end of the work He came to do. They, His twelve, are in the same steam of providence and will be protected. "Don’t be anxious," He tells them, "I will put into your mouths what you are to say, I will bring into your memories the incidents to tell to the people".
Here is a listing of the chapters and verses in John where such things are said: John 14:1-3, 10, 16-18, 26-28, 15:11, 16, 26-27, 16:7, 13-15, 22, 26-27, 33. Or simply read the three chapters and pick out your favorites.
A marvelous gift is mentioned in Matthew 10:13, "But blessed are your eyes for they see and blessed are your ears, for they hear…".
In the book of Acts, the Lord vividly shows the apostles that when they speak in their Galileen dialect every listener will hear their words as his own language in his ears; not gibberish, but Arabic to the Arabs, Greek to the Greeks, and Latin to the Romans.
When Peter starts to preach to a gathering of sympathetic Jews he speaks clearly and unafraid, saying that Jesus of Nazareth was the Son of God and that people should worship Him openly and repent of how they might have felt earlier. Peter’s talk in Acts 3 and 4 is a bold and powerful one. No more hiding behind locked doors.
The early history of the Christian church shows just how well all this worked out. You know what? The Apostles preached to the peoples in the Near East 2000 years ago, and their preaching is just as relevant today as it was then: "Repent for the kingdom of heaven is at hand." Being at hand has nothing to do with the date or the state of political history in the world, it has to do with the inside of your mind. The Lord is just as close to you now as He was then, and He never turns away, though we might turn away from him. Remember that He said "behold I stand at the door and knock and if anyone hears and opens the door He will come right in." This hasn’t changed nor will it ever change, but He leaves us in freedom to ignore His knocking, if that is what we want. We have to make the choice, but He is always ready if we choose to open the door.