Is it obligatory to wash the beard that is below the chin—that is, between the chin and the neck—if the beard does not show the skin of the face?

If the beard is sparse and the skin beneath it is visible, then it must be [combed through or] run through with the fingers (takhleel) so that the water reaches the skin. However, if it is dense and what is beneath it cannot be seen, then it is sufficient to wash its outer surface.

It is obligatory to wash what hangs down from the beard (what extends beyond the boundaries of the face), even if it is long.

As for what grows beneath the chin, it is not obligatory to wash it, because it is not included within the boundaries of the face.