Adam Clarke

Apelles, approved in Christ - A man who, on different occasions, had given the highest proofs of the sincerity and depth of his religion. Some suppose that Apelles was the same with Apollos: whoever he was, he had given every demonstration of being a genuine Christian. Of Aristobulus' household - It is doubted whether this person was converted, as the apostle does not salute him, but his household; or as the margin reads, his friends. He might have been a Roman of considerable distinction, who, though not converted himself, had Christians among his servants or his slaves. But, whatever he was, it is likely that he was dead at this time, and therefore those of his household only are referred to by the apostle.