God forewarns his people about the coming day of judgment, in order that the wicked might turn from their sin and be saved. For God has no delight in the death of the wicked, but desires that they should all repent (2 Peter 3:9). It also reminds the faithful to strive for holiness and godliness (2 Peter 3:11), and to be alert and watchful, living in constant readiness for the unexpected day to come.
3 And you shall tread down the wicked, for they will be ashes under the soles of your feet, on the day when I act, says the LORD of hosts.