Psalm 90:4
2 Even before the mountains came into existence, or you brought the world into being, you were the eternal God. 3 You make mankind return to the dust, and say, “Return, O people.” 4 Yes, in your eyes a thousand years are like yesterday that quickly passes, or like one of the divisions of the nighttime. 5 You bring their lives to an end and they “fall asleep.” In the morning they are like the grass that sprouts up: 6 In the morning it glistens and sprouts up; at evening time it withers and dries up.
2 Peter 3:8
6 Through these things the world existing at that time was destroyed when it was deluged with water. 7 But by the same word the present heavens and earth have been reserved for fire, by being kept for the day of judgment and destruction of the ungodly. 8 Now, dear friends, do not let this one thing escape your notice, that a single day is like a thousand years with the Lord and a thousand years are like a single day. 9 The Lord is not slow concerning his promise, as some regard slowness, but is being patient toward you because he does not wish for any to perish but for all to come to repentance. 10 But the day of the Lord will come like a thief; when it comes, the heavens will disappear with a horrific noise, and the celestial bodies will melt away in a blaze, and the earth and every deed done on it will be laid bare.
Notes and References
"... The text of 2 Peter first cites Psalm 90:4 and then remarks that God delays judgment to give time for repentance because He is merciful. (Compare Genesis Rabbah 22:1; Sirach 18) Although R. Joshua’s remarks were not strictly apologetic in function, they do situate Psalm 90:4 within the context of the delay of divine judgment and mercy which are also found in 2 Peter 3:8-9. As regards the conclusion of the world, “one day is as a thousand years” occurs both in discussions of the length of the messiah’s day, and in explanations of the length of the world. In one text, the thousand-year day is described as a day of vengeance according to Isaiah 63:7 ..."
Neyrey, Jerome H. The Form and Background of the Polemic in 2 Peter (pp. 407-431) Journal of Biblical Literature, Vol. 99, No. 3, 1980