Acts 21:23

Do therefore this. The Jerusalem leaders believed that the advice they were giving was for the best. There was no intent to involve Paul in trouble, but rather to counteract the prejudice against him, for which they seemed to think he was in some way to blame (AA 403). They should rather have recognized that God had worked mightily through Paul, and endeavored, themselves, to counteract the opposition to him.

Four men. These four men were evidently members of the Jewish Christian community, another illustration of the hold that the Jewish ceremonies still had upon the converts in Judea. The four Jewish brethren were already part way through the accomplishment of their vows, but another was permitted to join them under such circumstances, particularly if he bore the expenses of those already performing their vows.