On the way to the Garden of Gethsemane after celebrating the Passover with His disciples, Jesus warned according to Scripture that they would all fall away and be scattered that very night like sheep whose Shepherd was struck down (Mat 26:31). To this Peter boasted he would never fall away even if everyone else did (Mat 26:33), and was ready to go with Him both to prison and death (Luk 22:33). But even though Peter’s spirit was willing, Jesus also knew that his flesh was beset with weakness being unseasoned by prayer. What did Jesus then say to Peter in response? See Joh 13:38, Mat 26:34. What does Jesus’ reply teach us about what He understood to be the inevitable result of putting confidence in the flesh apart from the spiritual strength to support such confidence that comes only through a devotion to prayer? Cf. 1Co 10:12. In what way did Peter’s bravado and self-confidence actually contribute to his later denial of Jesus? See Joh 18:26-27. How might that have turned out otherwise if, rather than sleeping, he had become more spiritually aware by spending time with Jesus praying in the garden to obtain God-confidence, as was demonstrated by Christ’s own example?
Was Peter alone in his failed profession of loyalty to Jesus? See Mat 26:35. What evidence do we have that Peter and the rest of the apostles took to heart the lesson learned from their inability to stand up for Jesus apart from keeping watch through prayer in order to overcome the weakness of their flesh? See Act 1:14, 2:42, 4:23-24,31, 6:4, etc… Should we suppose that we are any less capable of denying the Lord or falling away in time of trial as did those who had personally walked with and been taught by Jesus, apart from the prayer and devotion to God’s truth that is the only basis for such confidence?
What additional details of Jesus’ prophecy about Peter’s denial does Mark record? See Mar 14:30, and notice very literally that Jesus’ words were, “I say to you that you yourself, today, on this night, before the rooster crows twice (or a second time), will deny me three times”; cf. the KJV and NET. In light of the Jewish reckoning of the day beginning at sunset, and that they had just eaten the Passover and it was now late into the evening, what is the significance of His words today, on this night? Considering the immediately imminent nature of Jesus’ prophetic words to Peter, how much more important were His words shortly later in the Garden of Gethsemane to watch and pray, which Peter and the others shrugged off to fall asleep? Are we like that in discounting the plain warnings of Scripture of the imminent dangers of our weak flesh to stand for the Lord and shrugging off our need to watch and pray because our bellies are full and we have become sleepy in the spiritual darkness?
Consider Jesus’ perfect understanding of the fallen nature of man and the weakness of his flesh and inability to stand for truth apart from the spiritual discipline of keeping watch and praying that allows one to see through the darkness of the world to the light of the truth. Beyond this, what does the certainty and specificity of Jesus’ words to Peter that he would deny Him three times that very night indicate about His divine nature as the Prophet Moses foretold would come, Who being One with the Father understood not only the Father’s perfect timing of what was about to happen to Him that night, but what would also happen to His disciples and how they would respond?
What does the additional information of the rooster crowing twice indicate about Mark’s attention to detail, as well as his proximity to an eye witness of the events, who the early church understood was Peter himself? Why does it make sense that the other gospels would omit such a detail as superfluous? In fact, what does it indicate about how ignorant Peter really was of his own blindness and weakness, that even after being forewarned just hours earlier that it would happen, either didn’t recognize it or perhaps justified it away even while he was in fact denying Jesus not just once or twice, but three times, exactly as Jesus had foretold, and it wasn’t until the rooster crowed not once but a second time that he came to his senses and realized what had happened and how Jesus’ words to him had been literally fulfilled and he had been completely powerless to prevent it? Again, in light of what the world would consider a monumental failure on Peter’s part, what does Mark’s account, as told by Peter himself, say about Peter’s humility that made him so fit to be the leader of the twelve apostles?
 Peter imagined that in the hour of temptation he should come off better than any of them, and Christ tells him that he should come off worse… Those often fall soonest and foulest that are most confident of themselves. Those are least safe that are most secure. Matthew Henry.