Reference for Nedarim 91:3
היה אחד מן השוק מודר באחד מהם הנאה לא יכנס לחצר רבי אליעזר בן יעקב אומר יכול לומר לו לתוך של חבירך אני נכנס ואיני נכנס לתוך שלך
IF A MAN FROM THE STREET WAS FORBIDDEN BY VOW TO BENEFIT FROM ONE OF THEM, HE MAY NOT ENTER THE COURT. R. ELIEZER B. JACOB SAID: HE CAN MAINTAIN, 'I ENTER YOUR NEIGHBOUR'S PORTION, AND I DO NOT ENTER INTO YOURS. IF ONE IS FORBIDDEN BY VOW TO BENEFIT FROM HIS NEIGHBOUR, AND THE LATTER POSSESSES A BATH-HOUSE OR AN OLIVE PRESS LEASED TO SOMEONE IN THE TOWN, AND HE HAS AN INTEREST THEREIN, HE [THE MUDDAR] IS FORBIDDEN [TO MAKE USE OF THEM]; IF NOT, HE IS PERMITTED. IF A MAN SAYS TO HIS NEIGHBOUR, 'KONAM, IF I ENTER YOUR HOUSE', OR 'IF I PURCHASE YOUR FIELD,' AND THEN [THE OWNER] DIES OR SELLS IT TO ANOTHER, HE IS PERMITTED [TO ENTER OR BUY IT]; [BUT IF HE SAYS.] 'KONAM, IF I ENTER THIS HOUSE, OR 'IF I PURCHASE THIS FIELD,' AND [THE OWNER] DIES OR SELLS IT TO ANOTHER, HE IS FORBIDDEN.