Responsa for Menachot 61:7

איכא דאמרי אמר ליה לך קח מן העובד כוכבים קסבר יש קנין לעובד כוכבים בארץ ישראל להפקיע מיד מעשר והוה ליה מן הפטור על הפטור

It was taught: R'Simeon of Shezur related, Once my untithed produce got mixed up with tithed produce,<span class="x" onmousemove="('comment',' And since the greater part of this mixture was tithed produce the whole is deemed by the law of the Torah to be tithed produce, and is not subject to any further tithe at all. It is, however, subject to tithe by Rabbinic law. The interpretation adopted here is the second given by Rashi, which is indeed preferred by him.');">⁷</span> so I went and asked R'Tarfon about it and he advised me, Go and buy some [demai<span class="x" onmousemove="('comment',' V. Glos.');">⁸</span>

Teshuvot Maharam

Teshuvot Maharam