פירוש על קידושין 101:1

If one gives 2/10 of one’s produce as tithe, the produce is considered tithed and may be eaten. But the tithes themselves are ruined since we do not know which part is the tithe and which part is not. But why, Abaye asks, is the second tenth considered even potentially a tithe? If I can’t first separate 1/10 and then another 1/10 both as tithes (indeed, one cannot), then when both are separated at the same time, neither of them should be tithes? This seems to refute Rabbah.