Like Moses going up the mountain with three companions (Exodus 24:1,Exodus 24:9), so, in Matthew 17:1, Jesus takes with him up the mountain the same disciples who would be with him in the garden of Gethsemane (Matthew 26:37–46), so that they might see his glory (2 Peter 1:16–17).
The main reason for taking only these three disciples was the need for separation. What will take place in the transfiguration is meant for only a few eyewitnesses. The fact that the text says Jesus took
these men up the mountain shows Jesus’ purposefulness, willingly carrying out this part of his work in the presence of the same apostles who were also called on other occasions to see special events (Mark 5:37; Mark 14:33).
Just as Moses once went up the mountain with three companions (Exodus 24:1,Exodus 24:9), so Jesus here in Matthew 17:1 takes three disciples—the very ones would later also be present with him in the garden of Gethsemane during his humiliation (Matthew 26:37–46)—up the mountain so that they might witness his glory (2 Peter 1:16–17).1
The main reason for taking only these three disciples was the need for separation. What is about to take place with the transfiguration on the mountain is intended for just a few eyewitnesses, not for many. The fact that the text says Jesus took
these men up the mountain indicates purposefulness; Jesus willingly carries out this special part of his work in the presence of the same three apostles who were also called on other occasions to witness special events (Mark 5:37; Mark 14:33). The disciples who are here called to behold his glory will likewise also be witnesses of his struggle in Gethsemane.2
1 And after six days Jesus took with him Peter and James, and John his brother, and led them up a high mountain by themselves.