Galatians
Gal 6:3 If anyone thinks he is something, when he is nothing, he deceives himself. Boasting is ruled out by total depravity. “When he is nothing” could be seen as a condition, leaving open the possibility that some people aren’t nothing and, if so, this wouldn’t apply to them, but Paul elsewhere considers himself nothing (2Co 12:11). If Paul can’t deny this statement applies to him, I don’t think anyone can.
Gal 6:4 His reason to boast will be in himself alone and not in his neighbor. Since the major theme of the epistle is justification by faith, and considering the immediate context (vv. 3, 14), Paul cannot be saying people can boast before God about their good works. It’s possible Paul holds out a real sense in which we can be proud of our own work (though only as Christ works through us; cf. Ro 15:17–18), but even so the emphasis here seems to be more on examining our own work without comparing ourselves to others, and not getting caught in sin ourselves when we’re helping others be restored to repentance.
Gal 6:14 But far be it from me to boast. Boasting is ruled out by grace.