“A woman was there who for eighteen years had been crippled by a spirit; she was bent over, completely incapable of standing erect. When Jesus saw her, he called to her and said, "Woman, you are set free of your infirmity."” (Luke 13:11-12)

This time, Jesus did not wait for the woman’s plea and cured her initiatively. As Jesus can see through people’s hearts, perhaps he knew that this woman was not afraid to ask but rather she was willing to dedicate her suffering to God for the rest of her life.

In the Old Testament, diseases was often placed together with the devil, not because of the disease coming from the devil, but when someone gets sick the devil would easily impose temptation onto them. 

Jesus felt weak and hungry after he fasted for forty days and nights. The devil approached Jesus and said to him, “If you are the Son of God, command that these stones become loaves of bread.” (Matthew 4:3)

When Jesus was crucified, “Those passing by reviled him, shaking their heads and saying, "You who would destroy the temple and rebuild it in three days, save yourself, if you are the Son of God, (and) come down from the cross!"

Likewise the chief priests with the scribes and elders mocked him and said, "He saved others; he cannot save himself. So he is the king of Israel! Let him come down from the cross now, and we will believe in him. He trusted in God; let him deliver him now if he wants him. For he said, 'I am the Son of God.'” (Matthew 27:39-43)

God bestows upon humans with His grace to allow their souls to rest in peace with Him.
Rest in peace does not only refer to the afterlife but also to people on earth, so that humans’ souls can live in peace with God.

All of the holy deeds are done only for the benefits of humans' souls.