John Calvin Commentary Acts 28:15

"And from thence the brethren, when they heard of us, came to meet us as far as The Market of Appius and The Three Taverns; whom when Paul saw, he thanked God, and took courage." — Acts 28:15 (ASV)

When the brethren heard. God comforted Paul by the coming of the brethren who came out to meet him, so that he might more joyfully hasten to defend the gospel. And the zeal and godly care of the brethren is apparent in this: that they inquired about Paul’s arrival and went out to meet him. For it was at that time not only an offensive thing to profess the Christian faith, but it might also put their lives in danger. Nor did only a few men put themselves in private danger, because the hostility affected the whole Church. But nothing was dearer to them than their duty, in which they could not be negligent, lest they be considered sluggish and unthankful. It would have been a cruel act to neglect so great an apostle of Jesus Christ, especially since he labored for the common salvation.

And now, since he had written to them before and had voluntarily offered his service to them, it would have been an improper thing not to repay him with brotherly goodwill and courtesy. Therefore, the brethren, by this their dutifulness, testified their godliness toward Christ; and Paul’s desire was more kindled, because he saw fruit prepared for his steadfastness.

For though he was endowed with invincible strength, so that he did not depend on human help, yet God, who usually strengthens His people through other people, administered new strength to him by this means. Though he was afterward forsaken when he was in prison, as he complains in a certain place (2 Timothy 4:16), yet he did not despair but fought no less valiantly and manfully under Christ’s banner than if he had been guarded by a great army.

But the remembrance of this meeting served even then to encourage him, since he considered with himself that there were many godly brethren at Rome who were weak, and that he was sent to strengthen them. And there is no reason why we should marvel that Paul was emboldened at this time when he saw the brethren, because he hoped that the confession of his faith would yield no small fruit. For as often as God shows His servants any fruit of their labor, He, as it were, pricks them forward with a goad, so that they may proceed more courageously in their work.