The Lord knows how to deliver the godly out of temptations, and to reserve the unjust unto the day of judgment to be punished:
All Commentaries on 2 Peter 2:9 Go To 2 Peter 2
George Leo Haydock
AD 1849
To reserve the unjust unto the day of judgment That is, God many times does not punish the wicked in this life, he suffers them to run on in the ways of iniquity, with prosperity as to the enjoyment of a short and vain happiness in this world, but his judgments are most of all to be dreaded, when the punishments are reserved till the next life, as it will appear at the day of general judgment: and from the time of their death they shall be tormented in hell. (Witham)