“The good old days” have never existed in Christianity. Every generation has bucked against salvation by grace through faith in one way or another. Even with the Apostles at the helm, the draw back to self-righteousness and law-keeping was a constant temptation (see Acts 15 and Galatians 2). Fear of man is so powerful it can change a person’s theology in a split second. One minute they are rejoicing in what Jesus has finished on their behalf. The next minute they believe it’s too good to be true. Surely somewhere, somehow, people have to keep their part of the deal to be saved—or assured of their salvation.

Christians can argue theology all day long in theory, but what we believe about justification has consequences in real life. It plays out either in faith that rests in Jesus’s righteousness credited to our account, or destructive self-righteous legalism. If a Christian does not return over and over again to the assurance of justification by faith alone (either functionally or in theory), they are most likely exhausting themselves, and others, trying to earn what they already have.

This is where Martin Luther found himself when he discovered grace alone through faith alone in Christ alone. He was trapped in a world where Jesus was a name slapped on a money-making business for the religious elite. He was an earnest and dutiful monk, but it was never enough. He could never do enough to get to God—to feel justified. This made him resent God.

I greatly longed to understand Paul’s epistle to the Romans and nothing stood in the way but that one expression, ‘the justice of God’, because I took it to mean that justice whereby God is just and deals justly in punishing the unjust. My situation was that, although an impeccable monk, I stood before God as a sinner troubled in conscience, and I had no confidence that my merit would assuage Him. Therefore I did not love a just and angry God, but rather hated and murmured against him. Yet I clung to the dear Paul and had a great yearning to know what he meant.

Night and day I pondered until I saw the connection between the justice of God and the statement that “the just shall live by his faith.” Then I grasped that the justice of God is that righteousness by which through grace and sheer mercy God justifies us through faith. Thereupon I felt myself to be reborn and to have gone through open doors into paradise. The whole Scripture took on a new meaning, and whereas before the “justice of God” had filled me with hate, now it became to me inexpressibly sweet in greater love. This passage of Paul became to me a gateway to heaven.

In addition to God’s moral law (which church leaders only appeared to be keeping in Martin Luther’s day), the church added more laws for the people to keep. They practiced extortion by charging the people a fee for the promise of a place in heaven for their loved ones. Most of the people in Martin Luther’s day could not read the Bible for themselves, and were therefore subject to the interpretations of men. This led them to embrace the natural inclination of the human heart that the way to God was to keep the law well enough. The concept of Christ as a perfect sacrifice for sins had been replaced with Christ as an example of moral behavior. Once Martin Luther understood that the just shall live by faith, he could speak of little else—his theology had changed his activity and his outlook. His changed behavior was viewed as disobedience to the church leaders, but never had he been so obedient to God. That is because “without faith it is impossible to please God” (Hebrews 11:6).

Perhaps the clearest treaty on Sola Fide can be found in Martin Luther’s preface to the book of Romans. Here is an excerpt:

Faith is not that human illusion and dream that some people think it is. When they hear and talk a lot about faith and yet see that no moral improvement and no good works result from it, they fall into error and say, “Faith is not enough. You must do works if you want to be virtuous and get to heaven.” The result is that, when they hear the Gospel, they stumble and make for themselves with their own powers a concept in their hearts which says, “I believe.” This concept they hold to be true faith. But since it is a human fabrication and thought and not an experience of the heart, it accomplishes nothing, and there follows no improvement.

Faith is a work of God in us, which changes us and brings us to birth anew from God (cf. John 1). It kills the old Adam, makes us completely different people in heart, mind, senses, and all our powers, and brings the Holy Spirit with it. What a living, creative, active powerful thing is faith! It is impossible that faith ever stop doing good. Faith doesn’t ask whether good works are to be done, but, before it is asked, it has done them. It is always active. Whoever doesn’t do such works is without faith; he gropes and searches about him for faith and good works but doesn’t know what faith or good works are. Even so, he chatters on with a great many words about faith and good works.

The church has wrestled with faith and works for thousands of years. Like Cain, men and women want to bring their own works before God to be approved rather than what God requires—a substitute. We can expect the wrestling match to continue until Jesus returns, but “the just shall live by faith” (Romans 1:17).