He hears a light knock at the back door, opens it, and there are 2 nuns there. One says, Mr Bartender, can we impose upon you for a wee favor? Certainly, Sister, what is it?

Well, its not for us, you understand, its for Father Murphy. Hes suffering from a bad case of the constipation, and the only thing that helps the poor man out is a wee drop of whiskey.The other nun continues, Wed go to the shop, but gossips in this town being as they are, we thought wed ask you for this favor instead, as we know youre a discreet man and can keep a secret, as all bartenders do.

The bartender replies, Certainly, Sisters, Ill just be a moment. He returns and hands them an unopened bottle of some fine Scotch single-malt.

Later, he locks up and starts driving home, and what does he see, but the two nuns, walking down the middle of the road, weaving, and singing at the top of their lungs. He can see the bottle, and its all gone except for the last inch or two.

He pulls over and rolls down the window. Sisters! he exclaims. I thought you said that bottle was for Father Murphys constipation!

Oh, but it is, one replied. When we get back, and he sees us in this condition, he's going to s#hit himself!