Note 5 — MESSIAH,
Reading edition
Alluding to Isaiah vi. 6, 7. "Then flew one of the Seraphims unto me, having a live coal in his hand, which he had taken with the tongs from off the altar; and he laid it upon my mouth, and said, Lo! this hath touched thy lips." Milton had already made the same allusion to Isaiah, at the close of his Hymn on the Nativity:
And join thy voice unto the angel quire, From out his sacred altar touched with hallowed fire.—Wakefield.