Jamieson, Fausset and Brown on Matthew 17:25

25. He saith, yes--that is, "To be sure He does"; as if eager to remove even the suspicion of the contrary. If Peter knew--as surely he did--that there was at this time no money in the bag, this reply must be regarded as a great act of faith in his Master.

And when he was come into the house--Peter's.

Jesus prevented him--anticipated him; according to the old sense of the word "prevent."

saying, What thinkest thou, Simon?--using his family name for familiarity.

of whom do the kings of the earth take custom--meaning custom on goods exported or imported.

or tribute--meaning the poll-tax, payable to the Romans by everyone whose name was in the census. This, therefore, it will be observed, was strictly a civil tax.

of their own children, or of strangers--This cannot mean "foreigners," from whom sovereigns certainly do not raise taxes, but those who are not of their own family, that is, their subjects.