The epistles of the New Testament provide commentary on the Gospels. They articulate the doctrine and practice of the Church based on the life, death, and resurrection of Jesus Christ as the fulfillment of Old Testament Scriptures. It is therefore impossible to remove Jesus from the epistles.
It is easiest to apply the doctrine of the epistles to Jesus because they clearly speak about Him. There are a great many doctrinal passages, however, that directly address human beings rather than God. For example, sin is a human problem. God does not sin, which means that Jesus, who is fully God, does not sin. If Jesus does not sin, then how is the preacher supposed to apply passages about sin to Jesus? First, humanity’s sin problem is the reason for Jesus’ Incarnation. Therefore, a passage like Romans 3:9-20, which declares that no human being is righteous, provides the preacher with the awesome task of expounding the reason for and achievement of the sinless life and sacrificial death of Jesus. This is precisely what Paul proceeds to do in Romans 3:21-31.
Any doctrine about humanity must be applied to Jesus because Jesus Himself is human. Therefore, the similarities and differences between fallen humanity and Jesus need to be explored by the preacher. For example, Paul contrasts Adam as a type of Christ in Romans 5:12-21. According to these verses, human beings fall into one of two categories. Each person is either in-Adam or in-Christ.
Whatever the doctrine, it finds is fullest expression in a right understanding of Jesus. There is no doctrine that can stand outside of Christ, and therefore all doctrine must be applied to and through Jesus.
The more challenging parts of the epistles to apply to Jesus are the passages concerning the practice of the Church. These passages directly exhort believers to behave in a certain way. Similar to Jesus’ teaching in the Gospels, any exhortation to the Church in Scripture is an exhortation from Christ calling the Church to be like Christ. Therefore, anything asked of the Church has been perfectly exemplified by Jesus. Providing the congregation with an example from Christ’s life will strengthen the preacher’s message. Secondly, the ability to obey Christ’s commands is only possible because of the death, resurrection, and ascension of Jesus and the indwelling of the Holy Spirit. The congregation must be continually taken to the Cross and reminded of the Spirit’s ministry in their lives in order to avoid moralistic works based sermons.
The epistles fall apart if preached apart from Jesus. Both the doctrine and practice of the Church, which is found in the epistles, must be built on a strong foundation, which is Christ. Remove the foundation and the whole structure collapses.
 Clowney, All of Scripture, 49-50.
 For more on preaching Christ from the epistles read: Greidanus, Modern Preacher, chapter 12.