WCF 18.4.
True believers may have the assurance of their salvation divers ways shaken, diminished, and intermitted; as, by negligence in preserving of it, by falling into some special sin which woundeth the conscience and grieveth the Spirit; by some sudden or vehement temptation, by God’s withdrawing the light of His countenance, and suffering even such as fear Him to walk in darkness and to have no light: (Cant. 5:2, 3, 6, Ps. 51:8, 12, 14, Eph. 4:30, 31, Ps. 77:1–10, Matt. 26:69–72, Ps. 31:22, Ps. 88, Isa. 50:10) yet are they never utterly destitute of that seed of God, and life of faith, that love of Christ and the brethren, that sincerity of heart, and conscience of duty, out of which, by the operation of the Spirit, this assurance may, in due time, be revived; (1 John 3:9, Luke 22:32, Job 13:15, Ps. 73:15, Ps. 51:8, 12, Isa. 50:10) and be the which, in the mean time, they are supported from utter despair. (Micah 7:7–9, Jer. 32:40, Isa. 54:7–10, Ps. 22:1, Ps. 88)