שְׂרָפִ֨ים עֹמְדִ֤ים ׀ מִמַּ֙עַל֙ ל֔וֹ שֵׁ֧שׁ כְּנָפַ֛יִם שֵׁ֥שׁ כְּנָפַ֖יִם לְאֶחָ֑ד בִּשְׁתַּ֣יִם ׀ יְכַסֶּ֣ה פָנָ֗יו וּבִשְׁתַּ֛יִם יְכַסֶּ֥ה רַגְלָ֖יו וּבִשְׁתַּ֥יִם יְעוֹפֵֽף׃
Rashi on Isaiah
for Him i.e., to serve him, and so does Jonathan render: Holy servants are on high before Him.
Rashi on Isaiah
with two he would cover his face so as not to look toward the Shechinah.