This indicates a significant change in the ministry of Jesus as he goes to Jerusalem for the final time.
## the prophets ##
This refers to the Old Testament prophets.
## will be accomplished ##
"will happen" or "will occur"
## Son of Man ##
Jesus speaks of himself as "the Son of Man" and uses "he" to refer to himself.
## on the third day ##
This refers to the third day after his death. However, the disciples did not yet understand this, so it is best not to add this explanation when translating this verse.