Albert Barnes Commentary 2 Timothy 2:19

"Howbeit the firm foundation of God standeth, having this seal, The Lord knoweth them that are his: and, Let every one that nameth the name of the Lord depart from unrighteousness." — 2 Timothy 2:19 (ASV)

Nevertheless the foundation of God is sure. The margin reads steady. The meaning is that even though some had been turned away by the arts of these errorists, the foundation of the church which God had laid remained firm. Compare Ephesians 2:20: And are built upon the foundation of the apostles and prophets, Jesus Christ himself being the chief corner-stone.

As long as this foundation remained firm, there was no reason to be troubled by the few instances of apostasy that had occurred. Compare Psalm 11:3. It is not uncommon to compare the church to a building erected on a solid foundation (Ephesians 2:20–21; 1 Corinthians 3:9–10; Matthew 16:18).

Having this seal. Or rather, a seal with this inscription. The word seal is sometimes used to denote the instrument by which an impression is made, and sometimes the impression or inscription itself. A seal is used for security (Matthew 27:66) or as a mark of genuineness (Revelation 9:4).

The seal here is one that was affixed to the foundation. It seems to refer to an inscription on the foundation-stone that always remained there, indicating the character and design of the edifice. The allusion is to the custom, when erecting an edifice, of inscribing the name of the builder and the design of the edifice on the corner-stone (see Rosenmuller, Alte u. neue Morgenland, No. 405).

Thus, the church of Christ is a building reared by the hands of God. Its foundation has been firmly and securely laid, and on that foundation there is an inscription always remaining, which determines the character of the edifice.

The Lord knoweth them that are his. This is one of the inscriptions on the foundation-stone of the church, which seems to mark the character of the building. It always stands there, no matter who apostatizes. It is, at the same time, a fearful inscription—showing that no one can deceive God, that he is intimately acquainted with all who enter that building, and that in the multitudes who enter there, the friends and the foes of God are intimately known.

He can separate his own friends from all others, and his constant care will be extended to all who are truly his own, to keep them from failing. This has the appearance of being a quotation, but no such passage is found in the Old Testament in so many words.

In Nahum 1:7, the following words are found: And he knoweth them that trust in him; and it is possible that Paul may have had that in mind. However, it is not necessary to suppose that he intended it as a quotation. A phrase somewhat similar to this is found in Numbers 16:5, The Lord will show who are his, rendered in the Septuagint, God knoweth who are his; and Whitby supposes that this is the passage referred to.

But whether Paul had these passages in view or not, it is clear that he meant to say that it was one of the fundamental things in religion that God knew who were his own people, and that he would preserve them from the danger of making shipwreck of their faith.

And, Let every one that nameth the name of Christ depart from iniquity. This is the other seal or inscription that is on the foundation God has laid. The foundation has two inscriptions: the first implying that God knows all who are his own people, and the other, that all who are his professed people should depart from evil. This is not found in so many words in the Old Testament, and, like the former, it is not to be regarded as a quotation. The meaning is that it is an elementary principle in the true church that all who become members of it should lead holy lives. It was also true that they would lead holy lives; and amidst all the defections of errorists, and all their attempts to draw away others from the true faith, those who did avoid evil might be known to be the true people of God.

For "Let every one," see Psalm 97:10.