Yoma2: 2
מַעֲשֶׂה שֶׁהָיוּ שְׁנֵיהֶם שָׁוִין וְרָצִין וְעוֹלִין בַּכֶּבֶשׁ, וְדָחַף אֶחָד מֵהֶן אֶת חֲבֵרוֹ; וְנָפַל וְנִשְׁבְּרָה רַגְלוֹ. וְכֵיוָן שֶׁרָאוּ בֵית דִּין שֶׁבָּאִין לִידֵי סַכָּנָה, הִתְקִינוּ שֶׁלֹּא יְהוּ תוֹרְמִין אֶת הַמִּזְבֵּחַ אֶלָּא בַפַּיִס. אַרְבָּעָה פְיָסוֹת הָיוּ שָׁם; וְזֶה הַפַּיִס הָרִאשׁוֹן.
It once happened that two were even as they ran and ascended the ramp, and one of them pushed his colleague; he fell and his leg was broken. Once the Court realized that there was a danger, they instituted that they not remove [the ashes] from the Altar, except by lot.  There were four lots there; this is the first lot.