One of the most difficult tasks is to understand relationship of the law and the gospel to the believer. Ephesians 1:5 states that those who believe have been adopted as God's children. On the surface, the concepts of law and Gospel and sonship seem to exist in tension. But the Bible clearly teaches both ideas, so we must accept both ideas and deal with them in different lights and on different levels.
According to our understanding of law and gospel, we know that the law must convict the heart before it is prepared to receive the gospel. Only then can salvation occur in the heart. This process must continue for salvation to continue in the heart of the believer.
But after conversion, we also have a new relationship with God. This relationship has many different labels that mean the same thing: believer, Christian, child of God, son of God, etc. that I will refer to as sonship. When a person is converted to Christ, changes begin to occur. The person begins to love the things that God loves and hate the things He hates. He starts to grow in his relationship with his Heavenly Father and demonstrate the fruit of the Spirit. He discovers more and more inner sin, confesses it, becomes free from its power. This is illustrated by the example of many people in the Bible.
But there is a danger in this, since this progress can lead to spiritual pride, where the person feels good enough on his own and no longer needs the gospel. If you have any doubt that this can happen, you do not need to look far to find examples today. You will see the rankest kind of spiritual pride among some Christians. It would almost seem that God should just leave sinners in their wretched state so that they would always fully appreciate the forgiveness in the gospel.
But, God knows that only through this progress will the full extent of the law be made known to the sinner and allow him to see his tremendous need for the gospel. As our own love for God grows, it becomes ever more painful for us to sin against Him. Paul, even after tirelessly serving God through much suffering and tribulation, sensed the wretchedness of his sin more than ever and stated that he was the chief of sinners. Applied to a believer, the law now expects us to progress and grow in the grace and knowledge of God. When we stand still or regress, the law uses that condition to convict us of sin. An example is David. When he fell back into sin, he was brought under conviction and needed to repent. The law will have a greater impact in the process of conviction of sin and reliance on the gospel in the individual who loves God and has a personal relationship with Him.
We know that salvation only occurs when a person's trust is not placed in the carrying out of the law, but in the forgiveness available in Christ. Yet, many times in the Bible, those seeking salvation are given some command to carry out. For example, when the rich young ruler came to Jesus seeking eternal life, he was told to obey the commandments, then to give away all his wealth and to come and follow Him. What this example points out is that not every person seeking salvation will comprehend the full depth of the gospel immediately. Some will need to hear law directing them how to become a disciple of Christ. But since we don't have the insight that Christ demonstrated with the rich young ruler, the gospel should always be presented also so the sinner can know that his sins are forgiven. This is similar to the kernel planted in an infant at baptism. The child will start to grow and trust in this knowledge of the gospel. The same will happen with the convert. As he grows in the knowledge of God, he will come to rely more and more on the gospel as his only hope of justification, because the law will continue to work more fully convicting him of sin as he lives in the presence of a holy God.
A Lutheran will often speak of his salvation in terms of the gospel of forgiveness, which is timeless, looking outside of himself to God. In this way, salvation is experienced daily from this message and made personal in the sacraments. In this regard, our salvation is not referring in the past tense to a conversion experience, but in a timeless sense, referring to the gospel.
The idea of sonship is found in the Bible also. As evangelical Lutherans, we also believe in the idea of sonship, where salvation allows us to approach God as our Father. Sonship allows us to be children of God and have continual fellowship with Him. The Holy Spirit enters our heart and guides us.
But to the Lutheran, an understanding of law and gospel forms the foundation, and sonship is the house that is built on this foundation. In this way, Lutherans are different than many Christians and other churches that reverse these levels.
As a Christian, we should examine our lives to make sure we are exposed to both the law and the gospel. A pastor told me about a fellow pastor who had made a visitation to the home of a woman who was ill. When he arrived there, the woman was lying in bed, sobbing in sorrow. He began to read her every gospel promise he could find in the Bible. After a while, she grew quiet and seemed comforted. After asking her several questions, the pastor determined that her sorrow was caused by listening continually to religious television programs where the message was almost completely law. His instructions were to limit the viewing of these programs and balance it by reading more gospel verses. An excellent source of gospel messages is also found in many of the old hymns. We can learn something from this example for our own spiritual lives.