WCF 17.2.
This perseverance of the saints depends not upon their own free will, but upon the immutability of the decree of election, flowing from the free and unchangeable love of God the Father; (2 Tim. 2:18–19, Jer. 31:3) upon the efficacy of the merit and intercession of Jesus Christ, (Heb. 10:10, 14, Heb. 13:20–21, Heb. 9:12–15, Rom. 8:33–39, John 17:11, 24, Luke 22:32, Heb. 7:25) the abiding of the Spirit, and of the seed of God within them, (John 14:16–17, 1 John 2:27, 1 John 3:9) and the nature of the covenant of grace: (Jer. 32:40) from all which ariseth also the certainty and infallibility thereof. (John 10:28, 2 Thess. 3:3, 1 John 2:19)