isaiah 6:2 Above it stood the seraphims: each one had six wings; with twain he covered his face, and with twain he covered his feet, and with twain he did fly. - Free Bible Online

      2. stood--not necessarily the posture of standing; rather, were in attendance on Him [MAURER], hovering on expanded wings.
      the--not in the Hebrew.
      seraphim--nowhere else applied to God's attendant angels; but to the fiery flying (not winged, but rapidly moving) serpents, which bit the Israelites (Nu 21:6), called so from the poisonous inflammation caused by their bites. Seraph is to burn; implying the burning zeal, dazzling brightness (2Ki 2:11; 6:17; Eze 1:13; Mt 28:3) and serpent-like rapidity of the seraphim in God's service. Perhaps Satan's form as a serpent (nachash) in his appearance to man has some connection with his original form as a seraph of light. The head of the serpent was the symbol of wisdom in Egypt (compare Nu 21:8; 2Ki 18:4). The seraphim, with six wings and one face, can hardly be identified with the cherubim, which had four wings (in the temple only two) and four faces (Eze 1:5-12). (But compare Re 4:8). The "face" and "feet" imply a human form; something of a serpentine form (perhaps a basilisk's head, as in the temples of Thebes) may have been mixed with it: so the cherub was compounded of various animal forms. However, seraph may come from a root meaning "princely," applied in Da 10:13 to Michael [MAURER]; just as cherub comes from a root (changing m into b), meaning "noble."
      twain--Two wings alone of the six were kept ready for instant flight in God's service; two veiled their faces as unworthy to look on the holy God, or pry into His secret counsels which they fulfilled (Ex 3:6; Job 4:18; 15:15); two covered their feet, or rather the whole of the lower parts of their persons--a practice usual in the presence of Eastern monarchs, in token of reverence (compare Eze 1:11, their bodies). Man's service a fortiori consists in reverent waiting on, still more than in active service for, God.

JFB.