O que segue é um trecho de um sermão de Martinho Lutero a respeito de Mateus 22:15-22. Está em inglês, pois assim o achei, e falta-me tempo para traduzir.
Thus one must also bear the authority of the ruler. If he abuses it, I am not therefore to bear him a grudge, nor take revenge of and punish him with my hands. One must obey him solely for God's sake, for he stands in God's stead. Let them impose taxes as intolerable as they may: one must obey them and, suffer everything patiently, for God's sake. Whether they do right or not, that will be taken care of in due time. If therefore your possessions, aye, your life and whatsoever you have, be taken from you by those in power, then you are to say: I give it to you willingly, I acknowledge you as my masters, gladly will I be obedient to you. Whether you use the power given to you by God well or ill, that is your affair.
But what if they would take the Gospel from us or forbid us to preach it? Then you are to say: The Gospel and Word of God. I will not give up to you. This is not within your power, for your rule is a temporal rule, over worldly matters; but the Gospel is a spiritual, heavenly treasure, and therefore your authority does not extend over the Gospel and God's Word. We recognize the emperor as a master of temporal affairs, not of God's Word; this we shall not suffer to be torn from us, for it is the power of God, Rom. 1, 16, against which not even the gates of hell shall prevail.
Therefore, the Lord beautifully summarizes these two things, and in one saying distinguishes them from each other: "Render unto Caesar the things that are Caesar's, and unto God the things that are God's."