R. Avrohom (from) Troy writes in the Hakdama to his sefer,
he once dreamt on Friday night Parshas Beshalach ,that he sat at a table
with a very old man who had a white beard and long hair.
The old man asked him who was the greatest Navi and R.AT
answered “Moishe Rabeinu.” He then asked why did Moishe wait
to say the Shira until after Kreias Yam Suf. All other Nevi’im said
the Nevua before the happening.
R.AT answered that Moishe Rabeinu was concerned that the
Bnei Yisroel who weren’t strong in their emuna won’t believe
him and won’t say the shira. He waited until after Krias Yam Suf.
Then it became Vayaminu Bahashem Uv’moishe avdo. Oz (when
they believed) Yoshir--.
"The old man accepted my answer with simcha."
R.AT continues that he always felt that the old man he saw in his
dream was Eliyahu Hanavi.
One day he (R.AT) saw the tshuvas maharam who writes the
Rabeinu Efraim (baalei hatosfos). had a dream
that an old man who was hairy (long hair) had a hadras ponim
and long beard, served him a bowel of insects.
R. Efraim asked him why was he serving him treifos. The old
man answered that being He eats Barbuta fish which is non kosher
he deserves a bowel of sherotzim. R. Efraim.said that the old man was
Eliyahu Hanavi and from then on he refrained eating Barbuta fish.
R.AT writes that after he saw this story and description of the old man
he became convinced that the old man he saw (with the long hair) in his
dream was Eliyahu Hanavi
*1 piyut motzei shabbos
*2 Part of this story is is brought down in Hagahos Oshri (Rosh avoda zarah
Perek 3 Siman 41)