1 And it came to pass that as the disciples of Jesus were journeying and were preaching the things which they had both heard and seen, and were baptizing in the name of Jesus, it came to pass that the disciples were gathered together and were united in mighty prayer and fasting.
2 And Jesus again showed himself unto them, for they were praying unto the Father in his name; and Jesus came and stood in the midst of them, and said unto them: What will ye that I shall give unto you?
There is power in the united prayers of believers. When we combine our faith and unite in prayer and fasting, Jesus will enter among us. We call down His Spirit into the midst of us. I have been in some meetings and especially in the House of the Lord when I have clearly felt His presence as a group of saints has "gathered together and were united in mighty prayer."
In this chapter, Jesus defines the gospel -- the good news. It is that He suffered for all who will repent of their sins, be baptized, receive the gift of the Holy Ghost, and endure in faith to the end of their lives. Jesus gives this promise:
16 And it shall come to pass, that whoso repenteth and is baptized in my name shall be filled; and if he endureth to the end, behold, him will I hold guiltless before my Father at that day when I shall stand to judge the world.
17 And he that endureth not unto the end, the same is he that is also hewn down and cast into the fire, from whence they can no more return, because of the justice of the Father.