And the Lord said, Simon, Simon, behold, Satan hath desired to have you, that he may sift you as wheat: But I have prayed for thee, that thy faith fail not: and when thou art converted, strengthen thy brethren. Luke 22:31-32 KJV
The sifting of wheat is illustrative: Wheat is placed in a sieve, which is shook from side to side so the chaff will rise to the surface, and then is blown away having no value. The goal of Satan in sifting Peter was to show that no faith of substance existed in him; he would be like chaff blowing in the wind. The warning of Jesus to Peter is one that all of us who profess to be Christians must be aware of, because Satan is out to take us apart as well (Peter 5:8). We have an enemy looking for an opportunity to take our faith apart, how important it is to be warned and on guard that our faith fails not. But do not miss the encouragement, Jesus was already praying for Peter, He prays for us too (Hebrews 7:25).
Lord, although I have an enemy looking for opportunities to destroy my faith, because You are so much greater than he is, I am comforted to know that You are already praying that I will be strengthened and that my faith will not ultimately fail.