Albert Barnes Commentary Acts 15:38

"But Paul thought not good to take with them him who withdrew from them from Pamphylia, and went not with them to the work." — Acts 15:38 (ASV)

But Paul thought not good. He did not think it proper. This was because he could not trust in his perseverance with them in the toils and perils of their journey.

Who departed from them, etc. Acts 13:13. Why he did this is not known. It was evidently, however, for some cause which Paul did not consider satisfactory, and which, in Paul's view, disqualified him from being their attendant again.

To the work. Of preaching the gospel.