When Jesus and his three main disciples come down from the mountain and meet the crowd waiting for him at the foot of the mountain (see Matthew 17:1), he again sees a person with a problem (Matthew 17:14), who shows that he is seeking help by kneeling before Jesus like someone seeking a favour. However, this posture is not one of worship, but rather of expectation in his desperate need. He asks not only for healing, as others had done in the past, but specifically for mercy (Matthew 17:15).
When the Saviour and his three main disciples came down from the mountain and met the crowd that had evidently waited for him at the foot of the mountain (see Matthew 17:1), he was immediately again confronted with a person with a problem (Matthew 17:14). His posture already clarifies that he is seeking help. He kneels before Jesus like a supplicant seeking a favour.1 This is why he falls down on his knees. We must not, however, interpret the posture in this context as one of worship, but rather as one of expectation from a man in desperate need2. Here the kneeling is not to make a simple request for healing, as many other parents and family members had done in the past, however, but he specifically pleads for mercy (Matthew 17:15).3
14 And when they came to the crowd, a man came up to him and, kneeling before him,