Responsa for Bava Metzia 33:4

אלא אי איכא לפלוגי הכי הוא דאיכא לפלוגי אמרו לו צא תן לו ואמר פרעתי והעדים מעידין אותו שלא פרעו (וחזר ואמר פרעתי) הוחזק כפרן לאותו ממון

then] the lender comes [to the Court and asks for a decree] to be written, [the decree] may be written and given to him. R. Zebid said in the name of R. Nahman: Whether [the Court said], 'Go [and] give him' or [it said] 'You are obliged to give him,' if [the debtor subsequently comes and] says, 'I have paid,' he is believed. [If then] the lender comes [to the Court and asks for a decree] to be written, [the decree] may not be written and given to him. If, therefore, [the wording of the Court's decision] is to make a difference [at all], the difference can only apply to the following cases: If they [the members of the Court] said to him [the debtor], 'Go [and] give him [what you owe him],' and he [the debtor] said [later], 'I have paid [as ordered],' and witnesses testify that he did not pay him,<span class="x" onmousemove="('comment',' Witnesses give evidence to the effect that following the order issued by the Court the plaintiff demanded payment from the defendant in their presence and was refused. As a consequence it is assumed that having defied the order of the Court in the presence of witnesses the defendant is not likely to have paid later in their absence, and he is not believed if he pleads subsequently 'I have paid'. ');">⁴</span>

Teshuvot Maharam