Mass. Gen. Laws ch. 67, § 16

If the person who is chosen collector is present and accepts the office, he shall forthwith be sworn. If not present, he shall be summoned to take the oath by a constable or by any person whom the clerk or assessors appoint for the purpose. Upon the refusal or neglect of a person present to accept such office at the time, or upon the neglect of a person so summoned, for the space of seven days, to appear and take the oath, the society shall proceed to a new choice; and so from time to time until some person accepts and is sworn.