In closing, Paul appealed to his readers to end the controversy in Galatia that had caused him so much trouble and distraction as Christ"s bond-slave. He cited the scars he had received as the target of persecution, in contrast to circumcision, as his final proof of his devotion to Christ (cf. Deuteronomy 15:17). He may have received some of these scars when the people of Lystra stoned him during his preaching tour of Galatia ( Acts 14:19-20; cf. 2 Corinthians 11:25). Paul was not a "people pleaser."[source]
"If a thing costs us nothing men will value it at nothing." [1][source]
"These genuine and honorable marks in the body contrast strikingly with the ritualistic and now meaningless mark (circumcision) the legalizers wished to impose on the Galatians." [2][source]
". . . Paul"s readers immediately would have identified the branding of the flesh with slavery, for slaves in the ancient world frequently were marked with the insignia of their master as a badge of identification." [3][source]
Paul finally appealed for God"s grace to be the portion of the Galatians (cf. Galatians 1:3). "Your spirit" means "you." As in no other of his epistles, he bid farewell by referring to his readers tenderly as "brethren."[source]
Whereas this epistle began very solemnly and harshly ( Galatians 1:6-9), Paul"s tone mellowed as he proceeded (e.g, Galatians 4:19). It ends on an uncommonly loving note (cf. Philemon 1:25; Philippians 4:23). [source][source][source]