Leviticus 10:8-11 "Do not drink wine or strong drink...when you enter the Tent of Meeting...and when you teach the children of Israel"

When a person drinks too much wine, it may cause him to think in an unclear manner. He may act silly and make incorrect decisions.

While in the Beit HaMikdash, we must conduct ourselves in a respectful and dignified manner.

It is forbidden to enter the Beit HaMikdash after having drunk wine or any other alcoholic beverage.

The same applies to a Rabbi making a decision about Torah Law.

He must be able to think very clearly and may not make such a decision after drinking wine.