Healed Instantly

Matthew 17:16-20 ESV

16 And I brought him to your disciples, and they could not heal him.” 17 And Jesus answered, “O faithless and twisted generation, how long am I to be with you? How long am I to bear with you? Bring him here to me.” 18 And Jesus rebuked the demon, and it came out of him, and the boy was healed instantly. 19 Then the disciples came to Jesus privately and said, “Why could we not cast it out?” 20 He said to them, “Because of your little faith. For truly, I say to you, if you have faith like a grain of mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move, and nothing will be impossible for you.”

The word translated here as heal could be used to speak of worship. The disciples could not heal the boy because they lacked faith. They could not heal because they were not fully healed themselves. This happened when the Holy Spirit was given at Pentecost. They then became true worshippers of God, for it is in spirit that worship takes place.  

θεραπεύω * therapeuō * ther-ap-yoo'-o * From the same as G2324; to wait upon menially, that is, (figuratively) to adore (God), or (specifically) to relieve (of disease): - cure, heal, worship.