שְׂרָפִ֨ים עֹמְדִ֤ים ׀ מִמַּ֙עַל֙ ל֔וֹ שֵׁ֧שׁ כְּנָפַ֛יִם שֵׁ֥שׁ כְּנָפַ֖יִם לְאֶחָ֑ד בִּשְׁתַּ֣יִם ׀ יְכַסֶּ֣ה פָנָ֗יו וּבִשְׁתַּ֛יִם יְכַסֶּ֥ה רַגְלָ֖יו וּבִשְׁתַּ֥יִם יְעוֹפֵֽף׃
Above Him stood the seraphim; each one had six wings: with twain he covered his face and with twain he covered his feet, and with twain he did fly.
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.