And teach customs
The Vulgate Latin and Ethiopic versions read in the singular number, "custom or law"; referring to the doctrine of salvation by Christ, in whose name the spirit of divination was cast out of the maid, and whom they took for a new deity; and so concluded that the apostle and his company were introducing a new religious law or custom, the worship of another God: which are not lawful for us to receive, neither to observe, being
for the city of Philippi was a Roman colony, and so the inhabitants of it called themselves Romans; or these men might be strictly such, who were transplanted hither; and with the Romans, it was not lawful to receive, observe, and worship, a new or strange deity, without the decree of the senate F12.
F12 Tertull. Apolog. c. 5. Euseb. Eccl. Hist. l. 2. c. 2.