שְׂרָפִים עֹמְדִים מִמַּעַל לוֹ שֵׁשׁ כְּנָפַיִם שֵׁשׁ כְּנָפַיִם לְאֶחָד בִּשְׁתַּיִם יְכַסֶּה פָנָיו וּבִשְׁתַּיִם יְכַסֶּה רַגְלָיו וּבִשְׁתַּיִם יְעוֹפֵף
Above Him stood seraphim; each one had six wings. With two he covered his face, with two he covered his feet, and with two he would fly.
The Talmud in Chagigah (16b) points out a contradiction between Isaiah’s vision and Yechezkel’s: our verse says that seraphim have six wings but Ezekiel 1:6 says they have four! The Talmud reconciles this by saying that they have six wings when the Temple is standing and four when it is not. (Remember that angels are spiritual being so it is perfectly reasonable that their appearance would reflect the state of holiness in the world at a given time.)