The disciples were afraid they were about to die, and Jesus seemed not to notice. Their danger was real. Barnes says they had set out "In the same boat, probably ill fitted to encounter a storm on the lake," and that "This would render their danger more imminent and the miracle more striking."

Their question sounds more like a protest than a prayer. Gill says they seem to have spoken "not so much praying and interrogating, as complaining and reproving." Still, they went to the right person. Matthew records their cry as "Lord, save us: we perish" (Matthew 8:25), and Luke as "Master, master, we perish" (Luke 8:24). Matthew Henry sums it up: "Their faith appeared weak, and their prayers strong."

Jesus answered first with action. "He arose, and rebuked the wind, and said unto the sea, Peace, be still. And the wind ceased, and there was a great calm" (Mark 4:39). Only then did He speak to the disciples, and He answered their question with questions of His own: "Why are ye so fearful? how is it that ye have no faith?" (Mark 4:40). The exchange ends with the disciples asking one another, "What manner of man is this?" (Mark 4:41).

The word "carest" translates melei, which Thayer defines as "it is a care" to someone. Martha uses the same word: "Lord, dost thou not care that my sister hath left me to serve alone?" (Luke 10:40). Peter uses it of God: "Casting all your care upon him; for he careth for you" (1 Peter 5:7).

Only Mark mentions the "hinder part of the ship" (the stern) and the "pillow," a cushion. Gill says Jesus slept there "being greatly fatigued with the work of the day." He had been teaching from a ship that same day (Mark 4:1, 35). "Master" here is Didaskale, "Teacher," which is why the ESV reads "Teacher."

The sleeping Jesus was truly tired, as Gill notes. The waking Jesus did what only God can do. Barnes says of His command to the sea, "None but the God of the storms and the billows could awe by a word the troubled elements." Both are true of the same Lord in the same boat.

The disciples' question, "carest thou not?", is answered by what Jesus did. He did not leave them to perish. Matthew Henry warns, "Those may suspect their faith, who can have such a thought as that Jesus careth not though his people perish." Yet the honest cry of frightened disciples was not turned away. Jesus calmed the storm first, and only then addressed their fear.