Mishnah — Seder Nezikin, Tractate ShevuotChapter 1…
“ Those of the Pilgrimage Festivals include more than them, for they atone for a pure person who ate an impure [food] item, and for [a sin while impure] that has no recognition either at the beginning or at the end; That of the Day of Atonement includes more than them, for it atones for a pure person who ate an impure [food] item, and for [a sin while impure] that has no recognition either at the beginning or at the end, and for [a sin while impure] that has no recognition at the beginning, but has recognition at the end ”
