Isaiah communicates his vision in symbolic terms. Just as Yahweh’s robe symbolically but not literally fills the temple, so these beings are symbolic.
Symbolism: “Seraphim” is plural, easily understood when Isaiah notes “each one.… ” The word is a transliteration of the Hebrew, meaning “burning ones.” This connotation has been lost in the translation, but “burning” would have illustrated their glory and marked them as celestial beings. Each seraph used its wings for flight, but its symbolic function—the more important—is to mark them as celestial beings. The heavens are above us, “in the air,” and therefore beings adapted to that realm would be “naturally” equipped with wings. Winged deities were frequently depicted not only in Jewish apocalyptic (see Ezek. 1:5–6, John 4:8), but also Egyptian and Babylonian religious art. The wings mark the wearer as one belonging to the heavenly realm. In the case of Isaiah, they are logical and fitting attendants to Yahweh’s throne.
Gileadi interprets this verse to stress the wings’ function as covering: “Seraphs stood by him overhead, each having six wings—with two they could veil their presence, with two conceal their location, with two fly about.” While “presence” and one’s “face” are associated in the scriptures (for example, “from thy face shall I be hid,” Gen. 4:14), and “feet” and “location” are logically connected, such functions appear somewhat irrelevant in this passage. Because Isaiah is looking at the seraphim, their location is not concealed, nor is their presence veiled. Isaiah sees them in Yahweh’s presence; before him the seraphim cover their faces and feet.
Another Old Testament episode in which an experience of glory results in covering is Exodus 34:33–35:
And till Moses had done speaking with them, he put a vail on his face.
But when Moses went in before the Lord to speak with him, he took the vail off, until he came out. And he came out, and spake unto the children of Israel that which he was commanded.
And the children of Israel saw the face of Moses, that the skin of Moses’ face shone: and Moses put the vail upon his face again, until he went in to speak with him.
The shining of Moses’s face and the “burning” aspect of the seraphim are caused by exposure to Yahweh’s glory. In Moses’s case, the veil not only conceals but also protects his people, who might be harmed by Yahweh’s overwhelming glory. Who is being protected in Isaiah’s case? It is not Isaiah, since he is already seeing Yahweh’s glory, which is necessarily greater than that of the seraphim. Rather, the seraphim are protecting their own faces. Yahweh’s glory is so great that even heavenly beings must be protected from its power.
Whether the feet connote earthly endeavors (Moses must remove his shoes on holy ground) or Blenkinsopp is correct in identifying “feet” as a euphemism for “genitals,” what Isaiah symbolically describes is the impact of Yahweh’s overwhelming glory.