Reference for Shevuot 91:2
א"ר ירמיה בר אבא שלחו ליה מבי רב לשמואל ילמדנו רבינו אומן אומר שתים קצצת לי והלה אומר לא קצצתי לך אלא אחת מי נשבע אמר להן בזו ישבע בעל הבית ויפסיד אומן קציצה ודאי מידכר דכירי אינשי
R'Jeremiah B'Abba said: The School of Rab sent to Samuel [the request]: Let our Master teach us: If an artisan says [to his employer]: 'Two [zuz] have you stipulated to pay me,' and the other says: 'I stipulated to pay you only one,' who takes the oath? - He replied to them: In this case the householder takes the oath, and the artisan loses, for the amount stipulated people certainly remember.<span class="x" onmousemove="('comment',' And we do not say that because the employer is busy with his labourers he does not remember the amount stipulated, and that therefore the oath should devolve on the labourer; but the employer takes the oath like every one who admits part of the claim.');"><sup>4</sup></span> But this is not so? For did not Rabbah B'Samuel learn: '[In the case of dispute about the amount] stipulated, he who desires to exact from his neighbour must bring proof'<span class="x" onmousemove="('comment',' Supra 45b.');"><sup>5</sup></span>