Till Abraham's time there was no such thing as a beard; but as many
mistook Abraham for Isaac, and Isaac for Abraham, they looked so exactly
alike, Abraham prayed to God for a beard to enable people to distinguish
him from his son, Isaac, and it was granted him; as it is written (Gen.
xxiv. 1), "And to Abraham a beard came when he was well stricken in
THE TALMUD, _Sanhedrin_, fol. 107, col. 2.