Paul had been making the point that, although the requirements of the law that God gave to Israel were good and just, they were ineffective as a means of providing salvation or eternal life, since no one was capable of perfect obedience to the law through their works.
If it had been possible for people to perfectly satisfy God’s requirement for holiness through their own efforts or actions, they would then be entitled to boast of this accomplishment, and consider themselves superior to others because of it.
However, because no one was capable of perfect obedience to the law of works, God in mercy made salvation and eternal life possible through Christ’s incarnation, sinless life, atoning death, and resurrection. The law of works has thus now been replaced by the law of faith, which grants salvation not on the basis of our actions but as a result of faith in Christ’s finished work of redemption to make us acceptable in God’s sight.
As a result (as Paul said), no one now has a right to boast of their own works as the means by which they have been saved, since salvation is gained entirely by faith in God’s actions (not our own), which puts everyone on an equal footing.
The “law of faith” is thus not a written code (as the law of works was), but the means by which God (through Christ) now grants eternal life, which opens the possibility of salvation to all (Gentiles as well as Jews).
Boasting is excluded because of the law that requires faith, not works, because to place our faith in Christ is humbling, whereas to claim any work earning us our Salvation would be boasting.
To say, “I placed my faith in Christ” or “I accepted Christ as my Saviour” isn’t something we can boast in, for by doing so we admit several things that are contrary to the nature of pride:
1) We acknowledge that we are sinners.
“This is a trustworthy saying, worthy of full acceptance: Christ Jesus came into the world to save sinners, of whom I am the worst. But for this very reason I was shown mercy, so that in me, the worst of sinners, Christ Jesus might display His perfect patience, as an example to those who would believe in Him for eternal life.” I Tim 1:15-16
By acknowledging our sin, we place the glory on Christ for His mercy in saving those who believe, not in anything we did. The proud will either not admit their sin (I John 1:8) or they will love their sin and hide from anything that might convict them regarding it (Jn 3:19-20)
2) We acknowledge that we are under condemnation for our sin and need rescue.
By placing our faith in Christ, we are humbly admitting that the just penalty of our sin is death (Rom 6:23, Jn 3:18) and hence we need saving. The proud will often deny they need saving at all.
3) We acknowledge that it is Christ alone who can save.
The proud will not admit that Christ is the only one who can save them and deliver them from death to life. If they believe they need saving at all, they look to themselves for saving (karma, good works, enlightenment, etc.)
4) We acknowledge that Christ saves us out of His mercy as a free gift to those who believe.
By acknowledging that salvation is a free gift offered by Christ, we humbly admit that it is not something ‘owed’ to us for our own merit, nor did Christ ‘have’ to die on our behalf to bring salvation. (Rom 6:23, Rom 5:16, Rev 22:17, Tit 3:5)
During Paul’s ministry, the fact the gospel was open and preached to Gentiles as well was a huge stumbling block for the Jews, who thought the Messiah was to come in power to overthrow Rome, not die to let Gentiles be reconciled to God. (I Cor 1:23-24) The fact that salvation was free, to all sinners, was also a stumbling block to the proud pharisees.
By placing our faith in Christ we submit to Him, dying to sin and self (I Pet 2:24-25, Eph 4:22, Col 3:9). We then, in humility, submit to Christ (Eph 5:24). Our whole lives become humble service to our King (Rom 12:1, Col 3:23-25, Heb 9:14) 6) Faith leads us to continual humility in regards to our fellow man Just as faith leads to a lifelong submission to Christ, so faith also leads us to submit to one another (Eph 5:21) and continually keep a proper perspective in our dealings with others in the church (II Cor 10:7-18, Gal 5:13)
“Let the one who boasts, boast in the Lord. For it is l not the one who commends himself who is approved, but the one whom the Lord commends.” II Cor 10:17-18
“For by the grace given me I say to every one of you: Do not think of yourself more highly than you ought, but rather think of yourself with sober judgment, in accordance with the faith God has distributed to each of you.” Rom 12:3
So then, faith is in every way contrasted with boasting, for it is based in humility, in a proper regard for one’s position in regard to Christ. If a man proclaims, “I have placed my faith in Christ!” this is not a boast, but humility, for he is testifying that, “I was a sinner under condemnation for my wicked deeds, one in need of Salvation, a salvation that only Jesus the Messiah could provide. I believe the Messiah is who He claims, with all authority given to Him. I have repented and given my life to Him, have died to myself and risen with him, and God for the sake of Christ’s righteousness and His glory shall grant me eternal life.”