Albert Barnes Commentary Luke 22:31

"Simon, Simon, behold, Satan asked to have you, that he might sift you as wheat:" — Luke 22:31 (ASV)

Simon. Peter. Jesus, foreseeing Peter's danger and knowing that he was about to deny him, took the opportunity to forewarn him and to put him on his guard, and also to provide him with solace when he would be brought to repentance.

Satan hath desired. Satan is the prince of evil. One of his works is to test the faith of believers—to place temptations and trials in their way, so that they may be tested. Thus God gave Job into his hands, so that it might be seen whether he would be found faithful, or would apostatize. (See Barnes on Job 1:7, and also Job 1:8-12.) So Satan desired to have Peter in his hands, so that he might also test 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 test 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 ardour and false professions.