Responsa for Bava Metzia 150:16
השוכר את האומנין וחזרו בהן ידם על התחתונה
OR LABOURERS TO REMOVE HIS FLAX FROM THE WATER OF STEEPING, OR ANYTHING WHICH WOULD BE IRRETRIEVABLY LOST,<span class="x" onmousemove="('comment',' If postponed. The bringing of pipers for a funeral or marriage is included in this category, because they are required for a particular time, and without them the ceremony suffers (Tosaf.). ');"><sup>28</sup></span> AND THEY [THE WORKERS] BREAK THEIR ENGAGEMENT;<span class="x" onmousemove="('comment',' Lit., 'withdrew' in the middle of their work. ');"><sup>29</sup></span> IF IT IS A PLACE WHERE NO OTHERS ARE AVAILABLE AT THE SAME WAGE, HE MAY HIRE [WORKERS] AGAINST THEM<span class="x" onmousemove="('comment',' I.e., at a higher wage. and claim the difference from the first. ');"><sup>30</sup></span> OR DECEIVE THEM.<span class="x" onmousemove="('comment',' This is discussed in the Gemara. ');"><sup>31</sup></span> IF HE ENGAGES ARTISANS AND THEY RETRACT [AFTER DOING SOME WORK]. THEY ARE AT A DISADVANTAGE;
Teshuvot Maharam
A. It is assumed that a person who might have gained an advantage by following a certain legal procedure, did not fail to follow such procedure. Since B could legally have been entitled to interest on his money had he granted the loan through a Gentile intermediary, we assume that he did grant the loan through such intermediary. Therefore, B is entitled to his interest and is not required to take an oath.
SOURCES: L. 197.