"And being in an agony he prayed more earnestly; and his sweat became like great drops of blood falling down to the ground." | Luke 22:44Matthew's and Mark's gospels say that Jesus went off three separate times to pray alone. Before he left, he asked his disciples to pray that they might not fall into temptation. Each time when Jesus returned he found Peter, James, and John asleep. Isn't that amazing? I believe we can gather two things from the disciples choice to sleep instead of pray. First, they must not have understood the reality of what was about to happen to Jesus. While he foretold of his death, their choice to sleep instead of pray reveals that they more than likely didn't understand what was about to happen to their LORD. Secondly, the disciples inability to stay awake reveals that they were were living in the flesh. When Jesus returned to his disciples after praying alone he said to Peter, “So, could you not watch with me one hour? Watch and pray that you may not enter into temptation. The spirit indeed is willing, but the flesh is weak” (Matthew 26:40-41). It was the disciple's flesh that was weak and Jesus knew that only by the Spirit could they find the strength and endurance they would need to resist temptation. And as we will later see, their lack of preparation would lead them to fall to all sorts of temptations (i.e. fear, deceit, doubt etc).
We all grow weary, both physically and spiritually, but just as he did for Jesus...the Holy Spirit is able to provide us the strength to endure even when our bodies physically can't do it on their own. Christ, found himself at a point of extreme agony. So what did he do? He prayed. Luke's gospel tells us that his sweat became like "drops of blood" falling to the ground. If anyone needed rest, it Jesus. And yet he knew better. He knew what he needed most could not be found in the comforts of physical rest. The strength Christ needed to endure "the cup" set before him could only be found in God himself...so he prayed.
And what can we take from Jesus' prayers? According to Matthew, the first time he prayed he said, “My Father, if it be possible, let this cup pass from me” (Mark 26:39). His desire was for God to provide another way. Jesus knew what he was about to endure. It was for this purpose that "Word became flesh and dwelt among us" (John 1:14). Christ came to die, but it was not death which caused Christ such agony. It was something far worse than death. Something Christ had never endured for all of eternity. Separation from his Father. Christ knew he would be taking on the wrath of God, that the sins of the world would be placed upon him. He also knew that because of sin, he would be separated and the loneliness and anguish of that separation would be far more than Jesus' physical body could handle. But the cup couldn't pass from Christ. This was the only way sin and death could be defeated and God's justice satisfied. So, instead of removing the cup from Christ...God sent an angel to come alongside Jesus to strengthen him (Luke 22:43).
Realizing that "drinking the cup" was the only way to reconcile a relationship between God's and man, Christ's second prayer took a very different tone. The second time he prayed he said, “My Father, if this [cup] cannot pass unless I drink it, your will be done” (Mark 26:42). The prayer was no longer relief from the agony, but instead that God's will be done. Christ's situation didn't change, but his perspective did. No longer was he left with simply agony. The angel of the LORD had given him strength to endure, and to see and embrace the future grace and glory. This was God's will, and Christ desired to live and die for his Father's glory.
"Jesus did not go on praying for the cup to pass. He went on praying for success in drinking it." | John Piper
Evidently, by the time Jesus was done praying in Gethsemane, the Father had not only made clear that there is no other way than the cross, but also that this way would succeed. The Lamb would have the reward of his suffering. He will “see his offspring; he will prolong his days; the will of the Lord will prosper in his hand. Out of the anguish of his soul he will see and be satisfied” (Isaiah 53:10–11).
Surely this is why Hebrews 12:2 could say, “For the joy that was set before him he endured the cross.” Beneath the terrors of present agony was the taste of future joy. The angel had come, “strengthening him” — clarifying, confirming, connecting the coming joy. -- source: DesiringGod.com