John Gill Commentary Acts 19:22

"And having sent into Macedonia two of them that ministered unto him, Timothy and Erastus, he himself stayed in Asia for a while." — Acts 19:22 (ASV)

So he sent into Macedonia
To Philippi, or Thessalonica, or Berea, or some of the places there, to let them know of his coming, and to prepare for him:

two of them that ministered unto him ;
that were his assistants in preaching the Gospel:

Timotheus and Erastus ;
the former of these was a disciple he found at Lystra, and took along with him, and to whom he afterwards wrote two epistles; and the latter seems to be the same with him, who was chamberlain of the city of Corinth, and is said to abide there, (Romans 16:23) (2 Timothy 4:20) The Ethiopic version, instead of Erastus, wrongly reads Aristarchus; whereas it is certain, he was not sent into Macedonia, but was with the apostle at Ephesus in the tumult, (Acts 19:29) .

But he himself stayed in Asia for a season ;
that is, at Ephesus, as the following narration shows.