In alluding to the prophet Isaiah in the prelude, Milton suggested that the iniquity of his lips had to be purged off -- burned off, with the live coal supplied by one of the seraphim.

弥尔顿在序曲中提到预言家艾赛亚，就是要表示他唇齿的邪恶,应该被净化，被其中一个，六翼天使用炭火烧掉。

耶鲁公开课 - 弥尔顿课程节选