Komentarz do Tohorot 2:4

הרביעי נאכל בנזיד הקודש (And [heave offering] in the fourth degree of ritual impurity is eaten in a pottage of Holy Things) – that is to say, that if there is in that heave offering fourth degree [of ritual impurity], as, for example, that was prepared in conditions of cleanness pertaining to Holy Things, and similarly the fifth degree [of ritual impurity] that is eaten in a pottage of Holy things, as is taught further on (in Mishnah 5 of this chapter) , this is how what he said: and if there is that Holy Thing fifth-degree [of ritual impurity] as, for example, that it was prepared in conditions of cleanness of a sin-offering of the ashes of the Red Heifer, as we stated, the clothing of those who consume Holy Things are [ritual impurity imparted] through treading (usually by someone with gonorrhea, a woman with an issue, a woman after childbirth and/or a menstruating woman) for a sin-offering is eaten in a pottage of Holy Things, it is permissible to combine in it a cooked dish of pure Holy Things.

Introduction Today's mishnah is the same pattern as yesterday's mishnah, except it deals with terumah. As we shall see, the rules governing terumah are one degree stricter than those governing common food.

First [degree] and second [degree uncleanness] in terumah are unclean and convey uncleanness; When it comes to terumah, even something with second degree uncleanness can defile other terumah.

Third [degree uncleanness] causes invalidity but does not convey uncleanness. Terumah with third degree impurity is invalid but it does not convey uncleanness to other terumah with which it comes into contact.

And fourth [degree uncleanness] may be eaten in a dish containing holy food. Basically, there is no such thing as fourth degree uncleanness when it comes to terumah. Something that has been in contact with third degree uncleanness can be eaten in a dish with holy food.