Moulana Ashraf Ali Thanwi saheb mentions that once an atheist said to Moulana Shah Ismail Shaheed saheb that the keeping of the beard is an extra and useless act. His proof for this was that since a person has no beard at the time of his birth, hence it should be forbidden to keep a beard.
Moulana Shaheed replied, "If that is the case then break your teeth as well."
Moulana Abdul Hayy saheb was there at the time as well, and he responded, "Wah Moulana! What a teeth shattering reply you gave!"
Adapted from Malfoozat Hakeemul Ummat
vol 12, pg 82