Then Jesus singles out Peter, but so that the others can hear. I use the old second-person singular to make the meaning clear:
Simon, Simon, listen! Satan has demanded to sift all of you like wheat. But I have prayed for thee, that thine own faith may not fail. And thou, when thou hast finally turned back, strengthen thy brothers. (Luke 22.31-32)
The verb that I translate here as “has demanded” means “has requested and his request has been granted.”
In other words, Jesus is saying that he has been privy to Satan’s insistence that he be able to test all of the Apostles (as we have seen, he has already done so with Judas). They have already weathered various peirasmoi with Jesus, but, since Satan’s request has been granted, more peirasmoi are coming, and they will be directed specifically towards the Apostles. All of the Apostles will succumb to these peirasmoi, Jesus indicates, including Peter, but Jesus’s prayers for Peter have ensured that his basic fidelity will remain in spite of his failure. And, once he has recovered himself, he will be in a position to help his fellow-Apostles regain their commitment. Peter acknowledges that he understands what Jesus is saying, because he vigorously denies that he will fail in any way: “Lord, I am ready to go with you to prison and to death!” Jesus responds by telling him just how he will fail a triple test, by denying him three times.
Our question must be, who was it that Satan made his demand to? Was it God? Was it Jesus himself? We cannot be sure. But the fact that his demand was granted demonstrates that Satan still has power and is still acting under the authority that has been given to him. It still remains part of the Divine Government that Satan test everyone on earth.