Spared not the old world,— This is put by a metonymy for the persons who lived before the flood, and perished in it; by way of opposition to the new world, or to mankind restored after that spreading desolation. Bishop Pearson would render the next clause, Noah, the eighth preacher of righteousness, but it seems very difficult, if not impossible, to make out that Noah was the eighth preacher. The Bishop adds, that if we are not disposed so to translate, it may be understood as denoting, not the order in which Noah was ranked, but merely the number of persons who were with him: Noah, with seven others; or Noah, one of the eight. And as this is true, so the calling him theeighth, in this sense, may be illustrated by authorities taken from several Greek writers. Heylin reads it, and preserved only eight persons, whereof the principal was Noah. God made more account of one righteous family, than of a whole generation of wicked persons. How could the false teachers and their wicked disciples hope to escape, when neither strength nor multitudes could defend the ungodly of former ages?—Or what need was there for the faithful to be terrified, when they were under the protection of that God, who had formerly delivered the righteous, how weak or few soever?
Related Commentaries of 2 Peter 2:5
2 Peter 2:5
5 And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly;