In the Old Testament, the role of the priest was of paramount importance in the religious and communal life of Israel. Priests were set apart to serve in the Tabernacle and later in the Temple, acting as mediators between God and the people. As such, they were subject to specific prohibitions and allowances to maintain their sanctity and effectiveness in their sacred duties.

Prohibitions:

1. Physical Defects: Priests were required to be without physical blemish to serve in the sanctuary. Leviticus 21:17-23 outlines that any descendant of Aaron with a defect was not permitted to offer the food of God. This included blindness, lameness, or any disfigurement.

2. Contact with the Dead: Priests were generally prohibited from coming into contact with dead bodies, which would render them ceremonially unclean. Exceptions were made for close relatives, as stated in Leviticus 21:1-4: "No one shall defile himself for a dead person among his people, except for his closest relatives."

3. Marriage Restrictions: Priests were restricted in their choice of a spouse. Leviticus 21:7 states, "They shall not marry a woman defiled by prostitution or divorced from her husband, for the priest is holy to his God." The high priest had even stricter requirements, as he was to marry only a virgin from his own people (Leviticus 21:13-14).

4. Consumption of Alcohol: Priests were forbidden from consuming wine or strong drink when entering the Tent of Meeting, as noted in Leviticus 10:9: "You and your sons are not to drink wine or strong drink when you enter the Tent of Meeting, lest you die."

5. Ritual Purity: Priests were required to maintain a high level of ritual purity. This included washing their bodies and garments, as well as avoiding anything that would make them ceremonially unclean (Leviticus 22:1-9).

Allowances:

1. Portion of Offerings: Priests were allowed to partake of certain portions of the offerings brought by the people. Leviticus 7:31-34 details the portions of the peace offerings that were allotted to the priests, including the breast and the right thigh.

2. Holy Garments: Priests were permitted to wear special garments that signified their holy service. Exodus 28 describes the intricate design of these garments, which included the ephod, breastplate, and turban.

3. Sabbath and Festival Observance: Priests were allowed to perform work on the Sabbath and during festivals, as their duties in the Temple were considered a necessary service to God (Numbers 28:9-10).

4. Cities of Refuge: Priests, along with the Levites, were given cities to dwell in, known as the Levitical cities. These included cities of refuge where individuals who committed manslaughter could seek asylum (Numbers 35:6-7).

5. Inheritance of the Lord: Unlike the other tribes of Israel, the priests and Levites did not receive a territorial inheritance. Instead, their inheritance was the Lord Himself, and they were supported by the tithes and offerings of the people (Numbers 18:20-24).

The prohibitions and allowances for priests underscore the distinct and sacred nature of their calling. These regulations were designed to ensure that the priests remained holy and set apart for their service to God and His people.