Tax often causes controversy.  In Jesus’ day, people paid taxes to the occupying Romans, and also a temple tax to the religious authorities (Mark 12:13-17).  Most adult males paid half a shekel (equivalent to two drachma) each year toward the upkeep of the temple.  Some (such as the Qumran sect) only paid once in a lifetime while others (the Sadducees) spoke strongly against the tax.  But it was not legally enforceable under Roman law, particularly as the shekel and half shekel coins were only used in the temple and were not common currency (the drachma was the common trading unit of money).  Jewish money changers made a business out of exchanging drachmas for shekels in the outer temple courts - later incurring Jesus' anger (Matthew 21:12-13).
 
When Peter was confronted by the money collectors, he said that Jesus did pay the tax.  We do not know if that was true, an assumption, or a convenient way of avoiding more discussion.  However, Jesus knew all about the conversation and used it to teach Peter another important lesson.  By asking him whether kings collected taxes from their children, Jesus was pointing to the fact that God is the King and the disciples were His spiritual children.  The maintenance of God's work did not ultimately depend on them, but Him.
 
However, Jesus did not want to get caught up in unimportant political controversy (Titus 3:9).  He ordered Peter to fish with a baited hook and line.  It was not the most common or productive of fishing methods, but the Lord only wanted one fish caught … the one He knew had a four drachma coin stuck in its mouth.  That coin would pay the tax for both Jesus and Peter.  It was a miracle.  In the hard times to come Peter would know that the Lord always provides enough to sustain both the ministry and the minister.
 
There is no point in frustrating God's work by pursuing issues that are not central to the gospel.  Financial matters easily fall into this category.  We need to learn that God provides, in His way.  He provides whatever is needed; and yet we should give freely so that others are not offended by our apparent hard-heartedness.  Let us pay taxes cheerfully (Romans 13:6-7), and make our gifts gladly and present our tithes in a timely manner.  Above all let us be encouraged that we are the children of God.  His love and generosity will never fail and His gospel will bring salvation to all who receive it.