Peter was comparing the disciples with the young man. Jesus had promised him "treasure in heaven" if he would sell all and follow (Matthew 19:21). He refused, but the disciples had done it. Barnes paraphrases Peter's thought: "We have done as thou didst command this young man to do. What reward may we expect for it?" Gill says Peter "lays hold on" Christ's words to the young man and asks what reward, what part in the kingdom, or what treasure in heaven would be theirs. Matthew Henry notes that what they left was "but a poor all, only a few boats and nets," yet Peter spoke as if it were some mighty thing.

Jesus answered with a solemn promise: "Verily I say unto you, That ye which have followed me, in the regeneration when the Son of man shall sit in the throne of his glory, ye also shall sit upon twelve thrones, judging the twelve tribes of Israel" (Matthew 19:28). He widened the promise to everyone who has forsaken houses, family, or lands "for my name's sake": they "shall receive an hundredfold, and shall inherit everlasting life" (Matthew 19:29). Then He added a warning: "many that are first shall be last; and the last shall be first" (Matthew 19:30), and went on to tell the parable of the labourers in the vineyard (Matthew 20:1-16).

Barnes thinks they probably left "nothing but their fishing-nets, small boats, and cottages. But they were their all." Matthew 4:18-22 records Peter, Andrew, James, and John leaving their nets and their ship to follow Jesus.

In Jesus' answer, Barnes notes that the word "regeneration" appears only once elsewhere in the New Testament (Titus 3:5). Here, he says, it probably means a great change, a "restoration of things" to a former or better state: the new order at the resurrection and judgment. He reads the twelve thrones as a figure of honor: "To sit on a throne denotes power and honor."

Jesus did not scold Peter for asking. Matthew Henry observes, "Christ does not upbraid them"; though they had left little, "it was their all," and Christ "accepts according to what a man hath." Gill agrees that Christ does not deny or despise what they gave up. God notices what His people leave behind for Him, and nothing given up for Jesus' name is lost (Matthew 19:29).

Yet Jesus also added a warning that runs into the next chapter: "many that are first shall be last" (Matthew 19:30). Barnes points out that the parable of the vineyard was spoken to explain this very saying (Matthew 20:1, 16). The reward is real, but it is given as God pleases, not as a debt we earn. Mark and Luke record Peter's words "we have left all" (Mark 10:28; Luke 18:28), but only Matthew records his question.