Reference for Shabbat 4:1
ידיעות הטומאה שתים שהן ארבע
the forms of consciousness of uncleanness are two which are four;<span class="x" onmousemove="('comment',' In Lev. V, 2f, 5-7 a variable sacrifice is also decreed for transgressing through uncleanness. According to the Talmud (Shebu. 7b) this refers to the eating of holy food, e.g., the flesh of sacrifices, and entering the Temple while unclean. Further, liability is contracted only if one was originally aware of his uncleanness, forgot it, and ate sacred food or entered the Temple, and then became conscious of it again. Thus there are two, viz., forgetfulness of uncleanness when eating sacred food, and same when entering the Temple. To these another two are added: forgetfulness of the sacred nature of the food and forgetfulness of the sanctity of the Temple while being aware of one's uncleanness. ');"><sup>1</sup></span>