New Defender's Study Bible Notes
21:21 forsake Moses. These were false charges, no doubt spread by the Jews who had opposed Paul in the cities of Asia where he had preached. Presumably many of these, like Paul, had come to Jerusalem for the festival of Pentecost, and stirred up the citizenry with these slanders when they saw Paul there. The stratagem devised by James and the Jerusalem elders to blunt these charges by having Paul associate himself with certain Jewish believers who had taken a Nazarite vow, even paying the expenses involved in the associated ritual, backfired. The very attempt to appease them by Paul was used by them to bring further false accusations against him, and to get him arrested.