Reference for Rosh Hashanah 27:2

ואי אשמעינן לכל אין בילה ה"א כרבנן ס"ל קמ"ל הלכה כר"ש שזורי

And if he had told us that mixing is not to be relied on for anything, I should have said that he holds with the Rabbis;<span class="x" onmousemove="('comment',' So that if old and new have become mixed together, tithe for both parts of the mixture must proportionately be given from some other quarter.');">²</span> therefore he tells us that the halachah follows R'Simeon Shezuri.

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