Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, Let every one that nameth the name of Christ depart from iniquity. The foundation of God standeth sure - The word θεμελιος signifies literally a foundation, and especially the foundation of a building; and metaphorically, the building itself, and often a noble mansion or palace. In this place the apostle compares the religion of Christ to a great or noble mansion. See 2 Timothy 2:20. And as this religion is founded on the authority and power of the Almighty, it necessarily must stand sure and be permanent. This house has an inscription on it, for so σφραγις, seal, is frequently understood; and this is evidently an allusion to the ancient temples. Above the door of the temple of Delphi there was the Greek word ει thou art, on which Plutarch has written an express treatise. In many of the Mohammedan mosques the walls are covered with inscriptions, which are ordinarily sentences taken from the Koran, relative to the majesty of God, or the nature of his worship. And we know that there was an inscription on the mitre of the high priest among the Jews, viz.: קדש ליהוה kodesh laihovah, "Holiness to the Lord;" Exodus 28:36; Exodus 39:30. See also Zephaniah 14:20. And this inscription may here be represented as being made with the seal of God, for he stamps this on all things belonging to himself and his worship.
But some suppose θεμελιος here to signify a contract or covenant by which two parties are bound to fulfill certain conditions and duties, the obligation to which, each takes on him by sealing the instrument with his seal. Among the Asiatics, these seals have scarcely ever any image or figure on them, but always some very expressive inscription. I have seen many of these, and several of them are now before me. The twofold inscription, i.e. one on the seal of each party, may be here alluded to; that on God's seal is, Εγνω Κυριος τους οντας αὑτου· The Lord approveth of them that are his. That on the seal of his followers is, Αποστητω απο αδικιας πας ὁ ονομαζων το ονομα Κυριου. Let every one who nameth the name of the Lord (every Christian) depart from iniquity. Thus each has his peculiar inscription.
Κυριου, Lord, instead of Χριστου, Christ, is the reading of almost all the MSS. of importance, and the principal versions.
The Lord knoweth - i.e. Approves, watches over, and provides for, them that are his true followers. To this his followers most cheerfully subscribe, and say: Let every one that nameth this Lord avoid every appearance of evil.