This chapter demonstrates the application of chapter 5:25 in the life of the Christian. Living in the Spirit, he will show spiritual love in the service of the church and in sincere devotion to the Lord Jesus Christ.
Mutual love is shown in the:
Restoration of a brother who fell into the error (v. 1). We are told in Ephesians 6:11 about the "wiles of the Devil" to cause the believer to fall into sin, which sometimes he only perceives after having fallen. He can then become discouraged and needs instruction given by a kindly spiritual Christian, who will take him in prayer to our High Priest to get forgiveness and restoration.
Fellowship and responsibility (v. 2-5). Fellowship with others in their burdens (difficulties, sorrows) and responsibility to faithfully fulfil our service to the Lord. Note the difference between "burdens" (costly weight) and "work" (labour, service).
Communion with instructors (v. 6). This continues the subject of v. 2, in relation to sharing the expenses of evangelical work, which is the duty of believers only and not of the world. We receive spiritual instruction and must contribute towards the expenses of the instructors. This is also the duty of believers with respect to the maintenance of the work of evangelization in general.
There is an inexorable rule concerning sowing and reaping (v. 7-10). The "harvest" always corresponds to what was sown (see also 2 Corinthians 9:6). He who acts to satisfy selfish and carnal desires and advantages will receive loss and sorrow in eternity; but he who spends his life according to the direction of the Spirit will reap the greatest benefits of eternal life.
Let us therefore fill our lives doing good, always and constantly, and especially to believers, who are our first responsibility; see 1 Timothy 5:8.
Note that verse 11 seems like an interruption in which Paul calls the reader’s attention to the "large letters" with which he wrote with his own hand (due to poor eyesight? See 4:14-15). The translation "long” or “large letter" does not seem right.
There is a false "glory" that comes from carnal pride: the Judaizers who taught circumcision to be obligatory for Christians were in reality seeking their own interests – the favour of the Jews and the exemption from persecution for being followers of the crucified Christ; also the "glory" of having converted many "pagans" to the regime of the Law, which the legalists did not keep themselves (v. 12-13).
There is, however, a true "glory" in which the apostle always wanted to walk - the glory that comes from belonging to Him who died on the cross of Calvary. After all, being Jewish ("circumcision") or Gentile ("uncircumcision") is not of any importance in the spiritual realm, the essential is to be born again in Christ to be "new creatures" (2nd Corinthians 5:17).
For all who walk according to this rule, Paul wants peace and mercy. They are the true "Israel of God", they are the "sons of Abraham" (see 3:9), saved by faith and not by works of the Law (v. 14-16).
"The marks of the Lord Jesus" (v. 17) are the end of the matter for Paul. The marks of wounds on his body, which he had received when persecuted in his evangelical work for love of the LORD, were of far greater value than the marks of circumcision in which the Judaizers gloried themselves!
The apostolic blessing emphasizes the grace of the Lord Jesus Christ (v. 18).
1 Brethren, if a man is overtaken in any trespass, you who are spiritual restore such a one in a spirit of gentleness, considering yourself lest you also be tempted.
2 Bear one another's burdens, and so fulfill the law of Christ.
3 For if anyone thinks himself to be something, when he is nothing, he deceives himself.
4 But let each one examine his own work, and then he will have rejoicing in himself alone, and not in another.
5 For each one shall bear his own load.
6 Let him who is taught the word share in all good things with him who teaches.
7 Do not be deceived, God is not mocked; for whatever a man sows, that he will also reap.
8 For he who sows to his flesh will of the flesh reap corruption, but he who sows to the Spirit will of the Spirit reap everlasting life.
9 And let us not grow weary while doing good, for in due season we shall reap if we do not lose heart.
10 Therefore, as we have opportunity, let us do good to all, especially to those who are of the household of faith.
11 See with what large letters I have written to you with my own hand!
12 As many as desire to make a good showing in the flesh, these would compel you to be circumcised, only that they may not suffer persecution for the cross of Christ.
13 For not even those who are circumcised keep the law, but they desire to have you circumcised that they may boast in your flesh.
14 But God forbid that I should boast except in the cross of our Lord Jesus Christ, by whom the world has been crucified to me, and I to the world.
15 For in Christ Jesus neither circumcision nor uncircumcision avails anything, but a new creation.
16 And as many as walk according to this rule, peace and mercy be upon them, and upon the Israel of God.
17 From now on let no one trouble me, for I bear in my body the marks of the Lord Jesus.
18 Brethren, the grace of our Lord Jesus Christ be with your spirit. Amen.
Galatians chapter 6