Reference for Chullin 270:7
רבן שמעון בן גמליאל אומר
are inextricably mixed up in it:<span class="x" onmousemove="('comment',' Even after they have divided between them the produce of the field, we do not assume that the share which each took eventually was intended for him from the beginning, so that the result would be that the Israelite's share is wholly tebel and the gentile's wholly hullin. This would mean the application of the principle of bererah i.e., retrospective designation. Rabbi does not accept this principle and maintains that each share, nay, each grain, is part tebel and part hullin; and the Israelite therefore must separate the tithe for his share from this very produce but not kcy from other produce, neither can this produce be set aside as tithe for other produce. V. Rashi s.v. vrhrc');"><sup>6</sup></span>