2 Peter 2:5

And spared not the old world. — The fact that the Flood is taken as the second instance of divine vengeance gives us no clue as to the source of the first instance. In the Book of Enoch the Flood follows closely upon the sin of the angels, as in Genesis 6 upon that of the sons of God, so that in either case the first instance would naturally suggest the second.

Noah the eighth person. — According to a common Greek idiom, this means Noah and seven others; and the point of it is that the punishment must have been signal indeed if only eight persons out of a whole world escaped. The coincidence with 1 Peter 3:20 must not pass unobserved, especially as there the mention of “spirits in prison” immediately precedes, just as here, the angels in “caves of darkness.” The suggestion that eight is here a mystical number (the sabbatical seven and one over) is quite gratuitous; as also that “eighth” may mean eighth from Enos, which would be utterly pointless, there being neither mention of Enos nor the faintest allusion to him. (Comp. Clement I. vii. 6; ix. 4; and see Note on 2 Peter 2:9.)

Bringing in the flood upon the world. — “In” should be omitted. The phrase is exactly parallel to “bring upon themselves swift destruction “in 2 Peter 2:1. The word for “bring” is the same in both cases.