“They who trust in Jehovah [shall be] like Mount Zion; it is not shaken; it remains forever. The mountains [are] all around Jerusalem; and Jehovah [is] all around His people, from this time and forever” (Psalm 125:1-2).
The Wicked Westminster Confession of Faith, in the section “Of Assurance of Grace and Salvation” (18.4), states:
“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: yet are they never so 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; and by the which, in the mean time, they are supported from utter despair.”
Those who doubt are “supported from utter despair” because they have NOT yet despaired of their own righteousness as the SOLE ground of acceptance before God. If they would despair of their own righteousness, and hope in the righteousness of Christ ALONE, they would never doubt, they would never be shaken, for they would have their foundation on the Rock of Jesus Christ:
“Only to God is my soul silent; from Him [comes] my salvation. He alone [is] my rock and my salvation, my strong tower; I shall not be greatly moved…Only be silent to God, O my soul, for my hope [comes] from Him. He alone [is] my rock and my salvation, my strong tower; I shall not be shaken. On God [is] my salvation and my glory; my strong rock, my refuge [is] in God” (Psalm 62:1-2, 5-7).
One’s assurance IS the ground of one’s salvation, and the ground of one’s salvation IS the ground of one’s assurance – Jesus Christ ALONE! The Spirit of God does NOT operate a self-righteous assurance in any allegedly “spirit-wrought fruit,” since the Spirit convicts God’s people of the truth that Jesus Christ and His righteousness is the ONLY ground of salvation and hence their ONLY assurance and hope of salvation.
“And when the Comforter comes, whom I will send to you from the Father, the Spirit of Truth who proceeds from the Father, that One will witness concerning Me” (John 15:26).
“And having come, that One will convict the world concerning sin, and concerning righteousness, and concerning judgment. Concerning sin, because they do not believe into Me; and concerning righteousness, because I am going to the Father, and you no longer see Me; and concerning judgment, because the ruler of this world has been judged” (John 16:8-11).
“But when that One comes, the Spirit of Truth, He will guide you into all Truth, for He will not speak from Himself, but whatever He hears, He will speak; and He will announce the coming things to you. That One will glorify Me, for He will receive from Mine and will announce to you” (John 16:13-14).
“For you did not receive a spirit of slavery again to fear, but you received a Spirit of adoption by which we cry, Abba! Father! The Spirit Himself witnesses with our spirit that we are children of God” (Romans 8:15-16).
“And because you are sons, God sent forth the Spirit of His Son into your hearts, crying, Abba! Father!” (Galatians 4:6).