“And behold, a leper came to him and knelt before him, saying, ‘Lord, if you will, you can make me clean.’ 3 And Jesus stretched out his hand and touched him, saying, ‘I will; be clean.’ And immediately his leprosy was cleansed.” (Matthew 8:2-3)
“And it has often cast him into fire and into water, to destroy him. But if you can do anything, have compassion on us and help us.’ 23 And Jesus said to him, ‘‘If you can’! All things are possible for one who believes.’ 24 Immediately the father of the child cried out and said, ‘I believe; help my unbelief!’ (Mark 9:22-24)
I find it interesting that the leper qualifying his request with “if you will” receives assurance, while the father of the demoniac who adds “if you can” receives a rebuke. The issue is not divine ability but divine willingness, and Jesus asserts both ability and willingness in these scenarios.
I think that these two stories taken together are an implicit argument against both truncated views of God that make him helpless but hopeful in the midst of human suffering (the God who wishes he could intervene but is for some reason a poor manager of the universe) and prosperity-Gospel views of God that portray him as eager to dispense health and wealth to any who have sufficient faith. Healing is not automatic; it is appropriate to pray “if you will.” But to add “if you can” is an offense.