אורח חיים קמ״חOrach Chayim 148

Se’if 1א׳

אֵין שְׁלִיחַ צִבּוּר רַשַּׁאי לְהַפְשִׁיט הַתֵּבָה בְּצִבּוּר כָּל זְמַן שֶׁהֵם בְּבֵית הַכְּנֶסֶת. פי' רַשִׁ"י שֶׁהָיוּ רְגִילִים לְהָבִיא סֵפֶר תּוֹרָה מִבַּיִת אַחֵר שֶׁהִיא מִשְׁתַּמֶּרֶת בּוֹ וְכו', עַד שֶׁטֹּרַח צִבּוּר הוּא לְהִתְעַכֵּב שָׁם, וְעַיֵּן בִּפְנִים בְּא"ח.

That the Prayer Leader May Not Uncover the Ark. Containing 1 S'if: The prayer leader does not have permission to uncover the Ark in [front of] the community - as long as they are in the synagogue. (Rashi explains that they were accustomed to bring the Torah scroll from another house where it was kept safe etc. and it was a burden on the congregation to have to wait there. See further inside in Orach Chaim)