Responsa for Nedarim 112:16

Q. A promised under oath to move out of T before the first of Iyyar or pay one mark to charity. The inhabitants of T claimed that A did not faithfully fulfill his promise, and they gave the following reasons: a) A did not move out of T since he had settled within the Sabbath limits (2000 cubits) of the town; b) he did not pay any taxes to the Cologne community, probably because he contended that he was still an inhabitant of T; c) he occasionally returned to T to collect his debts. Thus, A never intended to keep his promise; he was only trying to evade his oath; he, therefore, was obligated to pay one mark to charity. A, on the other hand, claimed that he had moved outside of the Sabbath limits of T into the jurisdiction of another overlord; that he had asked the tax collectors of Cologne to free him from the tax, because he had as yet not decided where to settle; that R. Jacob had told him that he, A, had fulfilled his promise properly; and that R. Jacob had, therefore, freed him from his obligation.
A. Even though A settled only within two thousand cubits of T, he had really moved out of T proper and had thus fulfilled his promise; for the outskirts of a town are not part of the town (as far as oaths or vows are concerned, cf. Ned. 56b). Moreover, it was just A's good fortune that he did not have to pay taxes to the Cologne community, because he was regarded as an inhabitant of T. We are in no position to determine whether or not A intended to keep his promise; and we have no right to fine A because of our suspicions or because we question his true intentions. However, in order to allay all suspicion, I advised A to make a statement, accompanied by a solemn hand-clasp, to the effect that he intended to fulfill his promise faithfully.
SOURCES: L. 217. Cf. Menahem of Merseburg, Nimmukim (2).