Yoma3: 1
אָמַר לָהֶם הַמְמֻנֶּה: ,,צְאוּ וּרְאוּ, אִם הִגִּיעַ זְמַן הַשְּׁחִיטָה”. אִם הִגִּיעַ, הָרוֹאֶה אוֹמֵר: ,,בַּרְקַאי”!  מַתִּתְיָא בֶּן שְׁמוּאֵל אוֹמֵר: ,,הֵאִיר פְּנֵי כָל הַמִּזְרָח”. ,,עַד שֶׁבְּחֶבְרוֹן”? וְהוּא אוֹמֵר: ,,הֵן.”
The administrator said to them, “Go out and see if the time for slaughtering has arrived.” If it had arrived, the one who sees [it] says, “Barkai!”  Mattisya ben Shmuel says: “The whole of the east has lit up.”  “As far as Hebron?”  And he says, “Yes!”