Jesus had asked them, "tarry ye here, and watch" (Mark 14:34), and they had fallen asleep. He spoke to Peter by name. Peter had boasted that he would never be offended and would die rather than deny Him (Mark 14:29, 31). Barnes says the appeal went to Peter "particularly on account of his warm professions, his rash zeal, and his self-confidence." Gill notes that Jesus called him Simon, "the name he first went by," not Peter, since he was not now showing "that firmness and constancy, though he boasted of it." The first question names what happened. The second asks how he lacked strength for even one hour. Gill draws out the point: "how will you be able to stand by me throughout this night, when ye cannot watch with me so much as one hour."

Mark records no answer from Peter. Jesus went on with a warning and a remedy: "Watch ye and pray, lest ye enter into temptation. The spirit truly is ready, but the flesh is weak" (Mark 14:38). He prayed again and came back to find them asleep again, "(for their eyes were heavy,) neither wist they what to answer him" (Mark 14:40). The third time He said, "Sleep on now, and take your rest: it is enough, the hour is come" (Mark 14:41).

The verb behind "couldest" is ischuo, which Thayer defines first as "to be strong," and the BibleHub interlinear renders it "were you able." Jesus' question asks whether Peter had the strength to stay awake for even one hour.

Barnes points out that Luke says Jesus found them "sleeping for sorrow" (Luke 22:45), meaning their grief was so great that they naturally fell asleep. He argues that their sleep was not indifference but "proof of their great attachment, and their deep sympathy in his sorrows."

Even in His own agony, Jesus cared for His sleeping friends. He had just prayed, "nevertheless not what I will, but what thou wilt" (Mark 14:36), and then He came to warn them, because temptation was close. That same night Peter would deny Him three times, just as Jesus had said (Mark 14:30, 66-72). Matthew Henry observes that believers often look at the Redeemer's sufferings in a drowsy manner, and "instead of being ready to die with Christ, they are not even prepared to watch with him one hour."

Jesus' words to Peter are honest and kind together. He named the failure, and He named the reason: "the spirit truly is ready, but the flesh is weak" (Mark 14:38). He did not leave Peter with only a rebuke. He told him what to do: watch and pray.