What does Mark 14:38 mean?
Jesus has just awakened Peter, James, and John who fell asleep while Jesus prayed in the garden of Gethsemane. Jesus has told them to "watch," meaning to pay close attention and avoid disaster. The verb tense used for "watch" and "pray" means that this is an on-going command. Jesus clarifies here that the disaster they should pray to avoid is sin."Spirit" is from the Greek root word pneuma. There are great debates about the exact nature of the heart, soul, mind, and spirit. Here, "spirit" is that part of a person that recognizes and interacts with the non-physical world. Its counterpart is the "flesh," which comes from the Greek root word sarx. Literally, the flesh is the physical part of a person; spiritually, it refers to the non-physical, sin nature of unbelievers and the unsanctified sinful impulses of a believer. That part of us that connects with God may have a desire to obey and follow Him, but the flesh does not have the strength to do good merely because God tells it to.
Without the work of the Holy Spirit, who gives us a new nature, the three disciples don't or can't abide Jesus' admonition to watch and pray against temptation. When Judas comes with the priests' guards to arrest Jesus, Peter acts. When he draws his sword and attacks, cutting off the ear of Malchus, the high priest's servant (John 18:10), he thinks he's revolting against the Jewish leadership, but he's really revolting against Jesus. Like his catastrophic, satanic failure in Mark 8:31–33, Peter rejects Jesus' march toward death and takes matters into his own hands to prevent it. Jesus again chastises Peter for attempting to keep Him from His Father's work (John 18:11). Jesus then heals Malchus, His enemy who has come to arrest Him and take Him to those who will condemn Him to death (Luke 22:51).
Jesus has already prophesied that Peter will deny that he knows Jesus (Mark 14:26–31). Peter's attack on the high priest's servant shows that he does not keep watch against temptation nor keep his faith in Jesus and God's plan. It is so easy to respond to fear by physically acting out when Jesus just wants us to have faith.
