Simon - Peter. Jesus, foreseeing the danger of Peter, and knowing that he was about to deny him, took occasion to forewarn him and put him on his guard, and also to furnish him with a solace when he should be brought to repentance.
Satan hath desired - Satan is the prince of evil. One of his works is to try the faith of believers to place temptations and trials in their way, that they may be tested. Thus God gave Job into his hands, that it might be seen whether he would be found faithful, or would apostatize. See the notes at Job 1:7-12. So Satan desired to have Peter in his hands, that he might also try him.
May sift you as wheat - Grain was agitated or shaken in a kind of fan or sieve. The grain remained in the fan, and the chaff and dust were thrown off. So Christ says that Satan desired to try Peter; to place trials and temptations before him; “to agitate him” to see whether anything of faith would remain, or whether all would not be found to be chaff - mere natural ordor and false professions.