3,983. Who Is an Onein?

Hilchos Bias HaMikdash 2:9

“Bereaved” means that someone has lost one of the relatives for whom he is obligated to mourn. On the day of that person’s death, he is considered an onein (bereaved) under Biblical law. At night, he is an onein under Rabbinic law.

Hilchos Bias HaMikdash 2:10

When one has to wait several days to bury his deceased, he is considered bereaved for all that time under Rabbinic law. This also applies to the day of the burial, but not to the subsequent night. Accordingly, if a close relative of a kohein dies and is buried after the day he died, the kohein may not offer or eat from sacrifices under Rabbinic law. He then immerses in a mikvah and may eat from sacrifices that night. The day on which someone learns that a close relative has died within the past thirty days and the day on which he exhumes the deceased’s bones for relocation are treated the same as the day of burial except the bereaved status isn’t extended to the night even by Rabbinic law. Such a kohein must immerse in a mikvah and he may eat from sacrifices that night. However, on the day of a close relative’s passing, just like one may not eat from sacrifices by day under Biblical law, it is likewise prohibited to eat from them that night under Rabbinic law. There is, however, one exception: the korban Pesach (Passover offering) may be eaten at night, as will be discussed IY”H in Hilchos Korban Pesach.