Is it permissible to sell to drunken customers?
Question

                My father has grocery shop and sometimes we have drunken customers that come in. I would like to know if it is permissable to deal with such customers and if by doing so it breaks wuduu as some of them smell strongly of alcohol or have cans of beer in their hand which they are drinking.
Praise be to Allah.We put the following question to Shaykh Muhammad ibn
    Saalih al-‘Uthaymeen:
A shopkeeper doing business in the West has Christians who come in,
    drunk or staggering, to buy things that are permissible. Is it permissible for him to sell
    to them?
He replied, may Allaah preserve him:
Yes, so long as they are Christian.
Question:
Why?
Answer:
It is permissible because the Christians believe that it is permissible
    to drink alcohol.
Question:
The question in our minds is that one of the two parties [engaged in
    the transaction] is not in his right mind.
Answer:
Does he not know how to make a purchase?
Question:
There are different types of drunkenness: a person may or may not be
    aware that he is buying something.
Answer:
If they are in such a state that they do not know (what they are
    doing), then it is not permissible to deal with them.
Question:
But if he is drunk and does know what he is doing?
Answer:
Then there is nothing wrong with it, as it says in the aayah
    (interpretation of the meaning):
“Approach not As-Salaah (the prayer) when you are in a drunken
    state until you know (the meaning) of what you utter” [al-Nisaa’ 4:43]
And Allaah knows best.