John Calvin Commentary 1 Corinthians 16:12

"But as touching Apollos the brother, I besought him much to come unto you with the brethren: and it was not all [his] will to come now; but he will come when he shall have opportunity." — 1 Corinthians 16:12 (ASV)

As to our brother Apollos. Apollos had succeeded Paul in the work of building up the Corinthians; therefore, Paul has in previous passages ascribed to him the office of watering. (1 Corinthians 3:6 and Acts 19:1). Paul now states a reason why Apollos does not come with the others, explaining this so that the Corinthians may not suspect that Paul had hindered him.

For the better Apollos was known by them, the more favorably they were disposed towards him, and so they would be more ready to conjecture that matters had been deliberately arranged for him not to go to them, in consequence of offense having been taken. They might, at least, be ready to ask among themselves: “Why has Paul sent these persons to us rather than Apollos?”

Paul answers that this was not his fault, since he entreated Apollos; but he promises that Apollos will come as soon as he has opportunity.