Wine

We learn from the incident of Nadav and Avihu a great deal about the consumption of wine. The standard explanation as to why they died, is because they entered the Holy of Holies intoxicated.

We know this because Aharon is commanded immediately after the tragedy this particular Halacha about not entering the קודש קדשים as שתויי יין, having drunk wine.

This is also the reason why Kohanim do not Duchan at Mincha every day. The assumption is that they may have drunk wine at lunch. This is why there is Duchaning, ברכת כהנים, on a fast day, as there is no lunch.

It is interesting that wine plays a dual role. On the one hand, wine is used in all religious ceremonies: Kiddush, weddings, Brit, פדיון הבן, etc. And yet, the Rabbis were very aware how wine was the vehicle to sinning and even intermarriage. They made special rules about not even allowing a Gentile to touch our wine.

This is but another proof where we see how there are two sides to each situation. The internet is another example. On the one hand, so much Torah is readily available. But on the other hand there is a great amount of impurity there as well. We need to learn how to make the right choices. Moderation is generally a good way to go-especially when talking about wine.