A seller of purple - Purple was a most valuable color, obtained usually from shellfish. It was chiefly worn by princes and by the rich, and the traffic in it might be very profitable. Compare the Isaiah 1:18 note; Luke 16:19 note.
The city of Thyatira - This was a city of Lydia, in Asia Minor, now called Akhisar. The art of dyeing was early cultivated in the neighborhood of Thyatira, as we learn from Homer (Iliad, iv. 141), and as is confirmed by inscriptions found in that city - a circumstance which may be referred to as confirming the veracity of the statements of Luke even in his casual allusions. Several of these inscriptions have been published. See the Life and Epistles of Paul, i. 295.
Which worshipped God - A religious woman, a proselyte. See the note at Acts 13:16.
Whose heart the Lord opened - See the note at Luke 24:45.