Mishnah for Bava Metzia 65:3

ה"נ מסתברא דקתני תחת משאו משאוי שיכול לעמוד בו מאן שמעת ליה דאית ליה האי סברא רבי יוסי הגלילי ש"מ

<i>'under its burden'</i> — a burden under which it can stand. Now, if you say that [relieving the suffering of an animal] is Biblically [enjoined], what does it matter whether it was lying [this once only], habitually lay down, or was standing? — The authority of this is R. Jose the Galilean, who maintained that [relieving] the suffering of an animal is [enjoined merely] by Rabbinical law. Reason supports this too. For it is taught: 'under its burden' — a burden under which it can stand. Now, whom do you know to hold this view? R. Jose the Galilean:<span class="x" onmousemove="('comment',' In the Mishnah supra 32a. ');">³</span>

Pirkei Avot