19 Nevertheless the solid foundation of God stands, having this seal: “The Lord knows those who are His,” and, “Let everyone who names the name of Christ depart from iniquity.”
20 But in a great house there are not only vessels of gold and silver, but also of wood and clay, some for honor and some for dishonor.
21 Therefore if anyone cleanses himself from the latter, he will be a vessel for honor, sanctified and useful for the Master, prepared for every good work.
22 Flee also youthful lusts; but pursue righteousness, faith, love, peace with those who call on the Lord out of a pure heart.
nevertheless (v.19) — in spite of the fact that the faith of some has been overthrown (v.18)
solid (v.19) = immovable
foundation of God (v.19) — According to the grace of God which was given to me, as a wise master builder I have laid the foundation, and another builds on it. But let each one take heed how he builds on it. For no other foundation can anyone lay than that which is laid, which is Jesus Christ. 1 Corinthians 3:10-11
stands (v.19) — tense indicates past action with continuing results
names (v.19) = utter a name as having special virtue, acknowledging what the name involves — a confession of allegiance
honor (v.20) = valuing, fixing a price — so “reverence, deference”
dishonor (v.20) — designated for common or base usage, ignominy, contempt
sanctified (v.21) — set apart for the worship and service of God. Not referring, here, to the sanctification that comes with salvation, but that which comes from growing in Christ and feeding the new nature.
useful (v.21) = easy to use, profitable
Master (v.21) = owner, one with undisputed ownership and authority
prepared (v.21 = equipped
lust (v.22) = craving, passionate desire — can be good or evil depending on the context
faith (v.22) = faithfulness, trustworthiness
love (v.22) = agape
My best shot at the meaning of this passage is this: It’s not always easy to tell who is and isn’t saved. Some who seem to have trusted Christ, but haven’t, can have their “faith” overthrown. Others who have truly trusted can be led into false doctrine and, therefore, fail to grow. But God knows those who have placed their faith in Christ. And those who have, and who realize what it means, will grow and will depart from iniquity. Verses 20 and 21 show that there are those who have believed but who are not fit for the Lord’s use because they allow themselves to be used contemptuously. To be fit for use, we must clean ourselves, flee from sin and actively, vigorously pursue righteousness in the company of others who are doing the same.