A.T. Robertson Commentary 2 Peter 2:9

"the Lord knoweth how to deliver the godly out of temptation, and to keep the unrighteous under punishment unto the day of judgment;" — 2 Peter 2:9 (ASV)

The Lord knoweth how (οιδεν κυριος). The actual apodosis of the long protasis begun in verse 4. God can deliver his servants as shown by Noah and Lot and he will deliver you. The idiomatic use of οιδα and the infinitive (ρυεσθα present middle and see verse 7) for knowing how as in Mt 7:11; James 4:17.

The godly (ευσεβεις). Old anarthrous adjective (from ευ and σεβομα, to worship), in N.T. only here and Ac 10:2,7 (by Peter). For

temptation (πειρασμου) see Jas 1:2, 12; 1 Peter 1:6.

To keep (τηρειν). Present active infinitive of τηρεω after οιδεν.

Unrighteous (αδικους). As in 1 Peter 3:18.

Under punishment (κολαζομενους). Present passive participle of κολαζω, old verb (from κολος, lopped off), in N.T. only here and Ac 4:21. Present tense emphasises continuity of the punishment. See κολασιν αιωνιον in Mt 25:46.