Truths given in the first three chapters serve as the foundation for applications in the last three chapters. The spiritual unity believers have in a church through the Father, Son, and Holy Spirit (vv. 4-6) must be guarded and promoted so that harmony and unity is seen and experienced (vv. 1-3). Christ provides for the unity of the church through spiritual gifts he has given (vv. 7-11). As members of a church minister to one another the whole body matures, is protected, grows, and is more united (vv. 12-16).

The church as Christ’s body must live like Christ in every area of human life (4:17-6:9). Believers must live like believers, not unbelievers (vv. 17-24). The “old man” (v. 22) refers to life as an unbeliever. Christians are not to lie (v. 25), be bitter or harbor grudges (vv. 26-27), should not steal but work (v. 28), and never use improper language but instead speak to edify others (vv. 29-32).

Truths to Nail Down and Meditate On

1. True unity can only be experienced through salvation from the Triune God. Sin is the root cause of every human problem in every human relationship. Efforts to deal with sin’s effects may bring a temporary appearance of improvement, but they are like putting a Band-Aid on skin cancer.
2. Christians have a deep responsibility to their brothers and sisters in their churches to strengthen and protect the unity God gives. Sadly, many Christians don’t take what God has done seriously when they don’t take their responsibilities seriously. Strengthening fellow-believers in a church is work, the work of the ministry that every Christian has (v. 12).
3. True salvation is seen in a night-and-day difference of life from that of unbelievers (vv. 17-32). This is because the change began with being born again, receiving new life in the heart (v. 18; cf. Prov 4:23).