On October 31, 1517 Martin Luther posted his 95 Theses on the door of the church in Wittenberg, Germany. Exactly 500 years later, I am celebrating the great movement of God that followed his initial protest by posting his comments in full on this great passage in Galatians 5:1-6, six posts in a row. Here's what he had to say about verse 3...
VERSE 3. For I testify again to every man that is circumcised, that he is a debtor to do the whole law.
The first fault with circumcision is that it makes Christ unprofitable. The second fault is that it obligates those who are circumcised to observe the whole Law. Paul is so very much in earnest about this matter that he confirms it with an oath. "I testify," he says, "I swear by the living God." Paul's statement may be explained negatively to mean: "I testify to every man who is being circumcised that he cannot perform the Law in any point. In the very act of circumcision he is not being circumcised, and in the very act of fulfilling the Law he fulfills it not." This seems to be the simple meaning of Paul's statement. Later on in the sixth chapter he explicitly states, "They themselves which are circumcised keep not the law. The fact that you are circumcised does not mean you are righteous and free from the Law. The truth is that by circumcision you have become debtors and servants of the Law. The more you endeavor to perform the Law, the more you will become tangled up in the yoke of the Law."
The truth of this I have experienced in myself and in others. I have seen many work themselves down to the bones in their hungry effort to obtain peace of conscience. But the harder they tried the more they worried. Especially in the presence of death they were so uneasy that I have seen murderers die with better grace and courage.
This holds true also in regard to the church regulations. When I was a monk I tried ever so hard to live up to the strict rules of my order. I used to make a list of my sins, and I was always on the way to confession, and whatever penances were enjoined upon me I performed religiously. In spite of it all, my conscience was always in a fever of doubt. The more I sought to help my poor stricken conscience the worse it got. The more I paid attention to the regulations the more I transgressed them.
Hence those that seek to be justified by the Law are much further away from the righteousness of life than the publicans, sinners, and harlots. They know better than to trust in their own works. They know that they cannot ever hope to obtain forgiveness by their sins.
Paul's statement in this verse may be taken to mean that those who submit to circumcision are thereby submitting to the whole Law. To obey Moses in one point requires obedience to him in all points. It does no good to say that only circumcision is necessary, and not the rest of Moses' laws. The same reasons that obligate a person to accept circumcision also obligate a person to accept the whole Law. Thus to acknowledge the Law is tantamount to declaring that Christ is not yet come. And if Christ is not yet come, then all the Jewish ceremonies and laws concerning meats, places, and times are still in force, and Christ must be awaited as one who is still to come. The whole Scripture, however, testifies that Christ has come, that by His death He has abolished the Law, and that He has fulfilled all things which the prophets have foretold about Him.
Some would like to subjugate us to certain parts of the Mosaic Law. But this is not to be permitted under any circumstances. If we permit Moses to rule over us in one thing, we must obey him in all things.
Luther, Martin. Commentary on the Epistle to the Galatians (pp. 142-143). Kindle Edition.