Thy disciples could not cure him - No wonder, when the cure must be effected by supernatural agency, and they had not faith enough to interest the power of God in their behalf, Matthew 17:20. A spiritual disorder must have a spiritual remedy: natural means, in such cases, signify just - nothing.

and they.

Matthew 17:19,20 Then came the disciples to Jesus apart, and said, Why could not we cast him out...

2 Kings 4:29-31 Then he said to Gehazi, Gird up your loins, and take my staff in your hand, and go your way: if you meet any man, salute him not...

Luke 9:40 And I sought your disciples to cast him out; and they could not.

Acts 3:16 And his name through faith in his name has made this man strong, whom you see and know: yes...

Acts 19:15,16 And the evil spirit answered and said, Jesus I know, and Paul I know; but who are you...

The Coin in the Fish's Mouth
'And when he was come into the house, Jesus prevented him, saying, What thinkest them, Simon? of whom do the kings of the earth take custom or tribute? of their own children, or of strangers? 26. Peter saith unto Him, Of strangers. Jesus saith unto him, Then are the children free.'--MATT. xvii. 25, 26. All our Lord's miracles are 'signs' as well as 'wonders.' They have a meaning. They not only authenticate His teaching, but they are themselves no inconsiderable portion of the teaching. They are not …
Alexander Maclaren—Expositions of Holy Scripture

1 to Pray is as it were to be on Speaking Terms with Me...
1. To pray is as it were to be on speaking terms with Me, and so by being in communion with and abiding in Me to become like Me. There is a kind of insect which feeds upon and lives among grass and green leaves and becomes like them in colour. Also the polar bear dwelling among the white snows has the same snowy whiteness, and the tiger of Bengal bears upon its skin the marks of the reeds among which it lives. So those, who by means of prayer abide in communion with Me partake, with the saints and …
Sadhu Sundar Singh—At The Master's Feet

Return to Galilee. The Passion Foretold.
^A Matt. XVII. 22, 23; ^B Mark IX. 30-32; ^C Luke IX. 43-45. ^b 30 And they went forth from thence [from the region of Cæsarea Philippi], and passed through Galilee [on his way to Capernaum]; and he would not that any man should know it. [He was still seeking that retirement which began on the journey to Tyre. See page 399. This is the last definite mention of that retirement, but we find it referred to again at John vii. 3, 4. See page 439.] 31 For he taught his disciples [the reason for his …
J. W. McGarvey—The Four-Fold Gospel