'What thinkest thou, Simon?'

'And while they abode in Galilee, Jesus said unto them, The Son of man shall be betrayed into the hands of men: and they shall kill him, and the third day he shall be raised again. And they were exceeding sorry. And when they were come to Capernaum, they that received tribute money came to Peter, and said, Doth not your master pay tribute? He saith, Yes. And when he was come into the house, Jesus prevented him, saying, What thinkest thou, Simon? of whom do the kings of the earth take custom or tribute? of their own children, or of strangers? Peter saith unto him, Of strangers. Jesus saith unto him, Then are the children free. Notwithstanding, lest we should offend them, go thou to the sea, and cast an hook, and take up the fish that first cometh up: and when thou hast opened his mouth, thou shalt find a piece of money: that take, and give unto them for me and thee.' (Matthew 17:22-27 KJV)

Peter could not have known how his master would pay tribute and offend not. He seemed to know that Jesus would, and could. But, until Jesus prevented (go before with spiritual guidance and help) him, Peter knew not how.

'Again I say unto you, That if two of you shall agree on earth as touching any thing that they shall ask, it shall be done for them of my Father which is in heaven. For where two or three are gathered together in my name, there am I in the midst of them.'

(Matthew 18:19,20 KJV)

Before I can agree with you, or you with me, each of us must first agree with Jesus Christ: how he paid tribute and offended not! THEN are the children free.