Reference for Yoma 160:7
ומי אמר רב פפא הכי והכתיב (ויקרא יא, מג) ולא תטמאו בהם ונטמתם בם וא"ר פפא מכאן שטומאת גוויה דאורייתא מדרבנן וקרא אסמכתא בעלמא
Is it not written: Neither shall ye make yourselves unclean with them, that ye should be defiled thereby.<span class="x" onmousemove="('comment',' Lev. XI, 43.');"><sup>7</sup></span> and R'Papa said that from here is derived the Biblical origin of the [laws concerning] the body's becoming defiled [through unclean foods]? - It is really Rabbinical, and Scripture is quoted only as mere [mnemotechnical] aid.<span class="x" onmousemove="('comment',' As far as Biblical law is concerned, a person could become defiled by food only by swallowing the meat of a ritually clean fowl that has died a natural death. The reference to this verse is used by R. Papa only to lend support to the more severe rabbinic law.');"><sup>8</sup></span>