Commentary for Kiddushin 82:13

ולר' שמעון דפטר דתנן תרומת עובד כוכבים מדמעת וחייבין עליה חומש ור"ש פוטר אתם גם אתם למה לי

for we learnt: A heathen's terumah creates a [forbidden] mixture,<span class="x" onmousemove="('comment',' I.e., if it falls into a quantity of hullin less than a hundred times as much as itself, and cannot be separated, the whole ranks as terumah, and is forbidden to an Israelite.');">²⁵</span> and one is liable to an [additional] fifth on its account.<span class="x" onmousemove="('comment',' If an Israelite eats terumah unwittingly, he must make restoration of the principal plus a fifth; Lev. XXII, 14.');">²⁶</span> But R'Simeon exempts [it]<span class="x" onmousemove="('comment',' Sc. the terumah separated by a Gentile on his crops from the law of terumah, i.e., he does not regard it as terumah at all.');">²⁷</span>

Daf Shevui to Kiddushin