_Bava Bathra_, fol. 16, col. 2.

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
age."

_Sanhedrin_, fol. 107, col. 2.

Here the word which the translators of the English version
render "was old," is taken in another of its cognate meanings as
a beard. The Midrash is a trifle more modest in this legendary
assertion. There we read, "Before Abraham there was no special
mark of old age," and that for distinction's sake "the beard was
made to turn gray."

When he died, all the chiefs of the nations of the world stood in a line
and exclaimed, "Alas for the world that has lost its leader! Alas for
the ship that has lost its helmsman!"

_Bava Bathra_, fol. 91, col. 2.

As Rabbi Banna went about to measure and to mark off the outward and
inward dimensions of the different caves, when he came to the cave of
Machpelah he found Eliezar, Abraham's servant, at the entrance, and
asked him, "What is Abraham doing?" The answer he received was, "He is
asleep in the arms of Sarah."