31 ¶ And the Lord said, Simon, Simon, behold, Satan hath desired to have you, that he may sift you as wheat:
32 But I have prayed for thee, that thy faith fail not: and when thou art converted, strengthen thy brethren. (Luke 22:31-32)
This little bit happened at the last supper as Jesus gave instructions to His disciples.
For a long time I wondered what was meant by “that he may sift you as wheat” and what was bad about it. In my head it evoked an image of a person with wheat on a screen and trying to force it through to strain out the non-wheat. But that confused me because it seemed more like a purification message. But Satan doesn’t want to purify us. So I knew I wasn’t getting something.
Finally, I realized that Jesus didn’t mean “putting through or filtering,” he meant the “shaking” part. Because sieves have to be shaken hard to get the wheat through. The image of sifting is that of trying to make us feel unstable in our faith and jerked back and forth by what's going on around us. That made a lot more sense. Satan does want to shake us; he wants to keep us from moving forward in faith.
Also, it was an appropriate time for Jesus to warn Peter of this. Jesus had preached that His followers were to have faith in Him, and then Jesus was about to allow Himself to be taken, tried, condemned, beated, mocked, whipped, and crucified to sacrifice His life. He knew it might shake their faith. He knew Peter, as chief apostle, would have an especially hard time with it.
The JST has another interesting bit. “Satan hath desired you, that he may sift the children of the kingdom as wheat.” This tells us that Satan didn’t just want to shake Peter; he wanted to take possession of him and thereby shake the rest of the kingdom of God. This tells us how important it is for leaders of the church to keep their faith strong so that they can help strengthen the rest of the church.
I think the verses also have two important principles to help when Satan tries to shake us: prayer (praying for ourselves and others) and preventing our faith from failing. Fervent prayer is a great way of re-orienting my wandering or sin-enticed or fearful thoughts toward Christ. Also, I know by experience that if I continue to act—keeping the commandments, doing my duty—that keeps my faith from weakening. Action builds faith, and faith leads to action. “Tis better far for us to strive, our useless cares from us to drive.”
I can also testify that our Heavenly Father continues to warn us of difficult experiences that we will have to face. I've seen that in my life. I haven't been warned of everything difficult, but I've been warned of enough things that I can testify of it. It has showed me that Heavenly Father knows the end from the beginning, that He knows me, and that He knows when a warning will help me better than allowing me to walk through it blindly. Getting the warning doesn't make me special, it just means that Heavenly Father knows I need it for my salvation and deliverance.