"So he with difficulty, and labour hard Moved on; with difficulty and labour he: But he once pass'd, soon after, when man fell, Strange alteration; Sin, and Death, amain, Following his tract (such was the will of heaven) Pav'd after him a broad and beaten way Over the dark abyss, whose boiling gulf Tamely endur'd a bridge of wondrous length, From hell contained, reaching th'utmost orb Of this frail world; by which the spirits perverse With easy intercourse pass to and fro, To tempt or punish mortals, except whom God and good angels guard by special grace." (Lines 1021-1033)