Responsa for Bava Kamma 82:4
ולהנך תנאי דמפקי ליה להאי בעל השור נקי לדרשה אחרינא [כדבעינן למימר קמן] הנאת עורו מנא להו
And now that the prohibition in respect both of food and of any [other] use has been derived from [the text] <i>'his flesh shall not be eaten'</i>, what additional teaching is afforded to me by [the words] <i>'The owner of the ox shall be quit'</i>? — [The prohibition of] the use of the skin. For otherwise you might have been inclined to think that it was only the flesh that had been proscribed from being used, whereas the skin should be permitted to be used; we are therefore told [that this is not the case but] that <i>'the owner of the ox shall be quit</i>.' But what of those Tannaim who employ this [text], <i>'The owner of the ox shall be quit'</i> for deriving other implications (as we will indeed have to explain <i>infra</i>);<span class="x" onmousemove="('comment',' V. pp. 236-239. ');"><sup>3</sup></span>
Teshuvot Maharam
A. B must take the oath usually taken by all partners, which is administered by the hazzan holding the Scroll of the law. Although giving one's faithful word is also considered an oath, it is not as solemn as the oath administered while holding the scroll of the Law, and can not take its place.
SOURCES: Cr. 171; Pr. 606; L. 379; Mord. Shebu. 765; cf. Hag. Maim. Shebuoth 11, 3; Moses, Minz, Responsa 17.