2 Timothy 2:19, 21
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. If a man therefore purge himself from these, he shall be a vessel unto honour, sanctified, and meet for the master’s use, and prepared unto every good work.
Paul found encouragement in the solid foundation of God. The foundation of God has a two-fold seal, as there is divine side and a human side. The divine side states that the Lord knows those who are His. God knows them, not only in the sense of recognition, but in the sense of possession. A seal is a mark of ownership and an emblem of guarantee and security. The seal also guarantees that all who have been converted will prove the reality of their new life by departing from unrighteousness.