The commandment of abstinence applies to the priests only during their times of service. They must be sober, self-controlled, and composed, so that they can be accurate and careful in performing the rituals assigned to them. They were also supposed to teach the people. When a layman would bring an offering and turn to a priest to perform it for him, the priest would give directions and explanations (see, e.g., Haggai 2:11–13). Thus, the priest has to be able to distinguish clearly and speak intelligibly.
9 Tu ne boiras ni vin, ni boisson enivrante, toi et tes fils avec toi, lorsque vous entrerez dans la tente d'assignation, de peur que vous ne mouriez: ce sera une loi perpétuelle parmi vos descendants,