But Paul thought not good - Did not think it proper. Because he could not confide in his perseverance with them in the toils and perils of their journey.
Who departed from them ... - 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 his view, disqualified him from being their attendant again.
To the work - Of preaching the gospel.