2 Peter 3:8

ὑμᾶς, emphatic, opposed to αὐτούς in 2 Peter 3:5.

Not only are the mockers mistaken as to the immutability of the world: they forget also (but you must not) that time is nothing in God’s sight. He delays His vengeance in mercy, but it will come.

μία ἡμέρα κ.τ.λ. The words go back to Psalms 90:4 χίλια ἔτη ἐν ὀφθαλμοῖς σου ὡς ἡ ἡμέρα ἡ ἐχθὲς ἥτις διῆλθεν, καὶ φυλακὴ ἐν νυκτί.

The writer does not apply the words in a sense which very usually attached to them among Jews and Christians. The belief arose (we cannot exactly trace by what steps), that since the world had been created in six days, and since a day and a thousand years are in God’s sight the same, so it would last six thousand years; and, as at creation the seventh day of rest followed, so the six thousand years would be succeeded by a seventh thousand of Sabbatical rest, the Millennium, as it is commonly called. We cannot dwell upon the importance of the belief in a Millennium: but the text before us was constantly invoked in support of that belief.