And when they came to the crowd, a man came up to him, and kneeling before him said, “Lord, have mercy on my son, for he is an epileptic and he suffers terribly; for often falls into the fire, and often into the water. And I brought him to your disciples, and they could not heal him.” And Jesus answered, “O faithless and perverse generation, how long am I to be with you? How long am I to bear with you? Bring him here to me.” And Jesus rebuked him, and the boy was cured instantly. Then the disciples came to Jesus privately and said, “Why could we not cast it out?” He said to them, “Because of your little faith. For truly I tell you, if you have faith as the grain of a mustard seed, you will say to this mountain, ‘Move from hence to yonder place,’ and it will move; and nothing will be impossible for you.”

Matthew 17:14-20

Through the care of this boy, Jesus teaches us the important role that faith plays in prayer. The strength of the comparison our Lord makes (v. 20) lies in the fact that a mustard seed is very tiny and yet can grow into a bush over three meters (ten feet) tall. Similarly, Christians, through their union with Christ, can share in the omnipotence of God. “Moving mountains” was probably a proverbial way of speaking, but it still conveys the idea that sincere prayer is very powerful.

This episode, coming just after the Transfiguration, also teaches us that “on the mountain” (see 17:1-5), when one is able to see the glory of the Lord, it is easy to have faith; but in the comings and goings of everyday life, belief can be more difficult (see v. 20). That is why the practice of our faith must be constant. We need to live by faith, and if we have vigorous faith, we will be able to go much further than if we rely on our own resources: “Though one in name, faith has two dimensions. One is the faith by which our soul assents to dogmas and teachings and our will attests to specific truths. The other dimension of faith is the which was given by Christ to some as a free gift, … a faith capable of performing works beyond any human power… Strive to live the faith that depends on your efforts and leads to the Lord who grants that faith to you, so that he may give you the other type of faith beyond any human strength or reckoning”.
("St. Cyril"of Jerusalem, Catecheses, 5, 10-11)

546

Jesus' invitation to enter his kingdom comes in the form of parables, a characteristic feature of his teaching.Through his parables he invites people to the feast of the kingdom, but he also asks for a radical choice: to gain the kingdom, one must give everything. Words are not enough, deeds are required. The parables are like mirrors for man: will he be hard soil or good earth for the word? What use has he made of the talents he has received? Jesus and the presence of the kingdom in this world are secretly at the heart of the parables. One must enter the kingdom, that is, become a disciple of Christ, in order to "know the secrets of the kingdom of heaven”. For those who stay "outside", everything remains enigmatic.

567

The kingdom of heaven was inaugurated on earth by Christ. "This kingdom shone out before men in the word, in the works and in the presence of Christ". The Church is the seed and beginning of this kingdom. Its keys are entrusted to Peter.

St. Thérèse of Lisieux

Our Lord never asks sacrifices from us beyond our strength. At times, it is true, this Divine Savior makes us feel all the bitterness of the chalice that He is offering our soul. When He asks the sacrifice of all that is precious in this world, it is impossible—without a very special grace—not to cry out like Him in the garden of agony… It is very consoling to think that Jesus, the Strong God, knew our weaknesses.

It is good to serve God in darkness and trial! We only have this life to live by faith.