Mishnayos Oholos Perek 1 Mishnah 3

כיצד ארבעה – vessels that come in contact with a corpse are progenitors of the primary sources of ritual impurity like it (i.e., a corpse). But a person [who is defiled] with utensils [which came in contact with a corpse becomes] a primary source of ritual impurity/אב הטומאה. And vessels [that were defiled by a corpse that came in contact with a person, is also a primary source of ritual impurity, like the person himself, as it is written (Numbers 31:24): “On the seventh day you shall wash your clothes and be pure, [and after that you may enter the camp],” hence you learned that every person who is defiled for seven days of defilement defiles vessels for a defilement of seven days.

הרביעי בין אדם בין כלים -become first-degree of ritual impurity. And the say law applies with “How so- for three?” for one is able to teach that a person who comes in contact with a corpse or vessels with a person are defiled with ritual impurity for seven days; the third, whether a person or vessels are defiled with ritual impurity until nightfall, but from the concluding clause [of the Mishnah] for the fourth who are defiled through contact with a corpse, we understand it, that even a person with utensils that came in contact with a corpse and/or vessels that came in contact with a person is taught that there is a period of defilement for seven days. All the more so, a person with the dead himself, or vessels with a [defiled] person, where there is a defilement of ritual impurity for seven days.

שפוד (a spit) – like a kind of column of metal that is fastened in the tent and upon its end they tie the tent.

אין האוהל מתחשב (the tent does not come into consideration)- because the tent does not defile the spit, therefore it is not considered in the number of the order of the defilements, but rather, all that is placed in the tent of the corpse is like it is touching the corpse itself, and there are only four here. Alternatively, even if the spit is not within the tent, but rather that it touches the tent from outside, nevertheless, the tent does not come into consideration in the number of the order of our Mishnah. And this proved further on/ahead in the Chapter "סכום עבה"/The Thick Coarse Woolen Blanket (Chapter 15), in the Mishnah "טבליות של עץ"/Tables of Wood (Mishnah 2).