Mishnah Meilah 4

¹Things dedicated for the altar combine with one another with regard to the law of sacrilege, and to render one liable over them [for the laws of] piggul, notar and defilement. Things dedicated for Temple repair combine with one another. Things dedicated for the altar combine with things dedicated for Temple repair with regard to the law of sacrilege. ²Five things in an olah combine with one another: the flesh, the fat, the fine flour, the wine and the oil. And six in a todah: the flesh, the fat, the fine flour, the wine, the oil and the bread. Terumah, terumah of the tithe, terumah of the tithe separated from demai, hallah and first-fruits combine with one another to make up the size required to render other things forbidden and to be liable for the payment of a fifth. ³All kinds of piggul can combine with one another and all kinds of notar can combine with one another. All kinds of carrion can combine with one another. All kinds of sheratzim can combine with one another. The blood of a sheretz and its flesh can combine with one another. A general rule was stated by Rabbi Joshua: all things that are alike both in respect of [duration of] uncleanness and in respect of their minimum measure can combine with one another. Things that are alike in respect [of duration] of uncleanness but not in respect of minimum measure, in respect of minimum measure but not in respect [of duration] of uncleanness, or [if they are alike] neither in respect [of duration] of uncleanness nor in respect of measure, cannot combine with one another. ⁴Piggul and remnant do not combine with one another because they are of two different names. Sheretz and carrion, as well as carrion and the flesh of a corpse do not combine with one another to effect impurity, not even in respect of the more lenient of the two [grades] of defilement. Food contaminated through contact with a primary defilement can combine with that contaminated by a secondary defilement to affect uncleanness according to the lower degree of defilement of the two. ⁵All kinds of food can combine with one another:To make up the quantity of half a peras in order to render the body unfit [To make up the food] for two meals to form an eruv; To make up the volume of an egg to contaminate food; To make up the volume of a dry fig with regard to carrying on Shabbat; And the volume of a date with regard to Yom Kippur. All kinds of drinks can combine with one another: To make up a quarter [of a log] in order to render the body unfit; To make up a mouthful with regard to Yom Kippur. ⁶Orlah and kilayim of the vineyard can combine with one another. Rabbi Shimon says: they do not combine. Cloth, sack-cloth, sack-cloth and leather, leather and matting combine with one another. Rabbi Shimon: What is the reason? Because these are all susceptible to the uncleanness caused by sitting.