IN THOSE DAYS, a certain man came to Jesus, knelt down before Him, and said, “Lord, have mercy on my son, for he has seizures (literally: lunatic) and he suffers terribly. He often falls into the fire and into the water. And I brought him to Your disciples, but they could not heal him.” Jesus answered, “Faithless and perverse generation! How much longer must I be with you? How much longer must I put up with you? Bring him to Me.” And Jesus rebuked the demon, and it came out of the boy, and he was healed instantly. Then the disciples came to Jesus privately and asked, “Why could we not cast the demon out?” He said to them, “Because of your unbelief. For truly I tell you, if you have faith even the size of a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move, and nothing will be impossible for you. But this kind of spirit does not come out except by prayer and fasting.” As they were staying in Galilee, Jesus said to them, “The Son of Man is going to be betrayed into human hands. And they will kill Him, and on the third day He will be raised.”
Origen on the perverse generation,
When the Savior says, "Faithless and perverse generation," He shows that wickedness has entered us through perversity, that it is contrary to nature and makes us perverse. And I think that He was irked at the whole human race on earth for its wickedness. So He said, "How much longer must I put up with you?"
And Saint Augustine talks about praying to cast out our own demons,
In this chapter the Lord urged us to pray when He said, "Because of your little faith you could not cast out this demon." For urging us to prayer He thus concluded, "This kind of spirit does not come out except by prayer and fasting." If you pray so that you may throw out someone else's demon, how much more so that you may cast out your own avarice? How much more so that you may cast out your own drunkenness? How much more so that you may cast out your own dissipation? How much more so that you may cast out your own impurity? How great are the sins in human being! If they persevere in them, they do not allow them to enter the Kingdom of heaven.
The Whole Counsel of God Bible study: