Question: May one who doubteth of his being in Christ, or of his due preparation, come to the Lord’s supper?
Answer: One who doubteth of his being in Christ, or of his due preparation to the sacrament of the Lord’s supper, may have true interest in Christ, though he be not yet assured thereof;[1] and in God’s account hath it, if he be duly affected with the apprehension of the want of it,[2] and unfeignedly desires to be found in Christ,[3] and to depart from iniquity:[4] in which case (because promises are made, and this sacrament is appointed, for the relief even of weak and doubting Christians[5]) he is to bewail his unbelief,[6] and labor to have his doubts resolved;[7] and, so doing, he may and ought to come to the Lord’s supper, that he may be further strengthened.[8]
Westminster Larger Catechism Q&A #172
Scripture references for further meditation:
[1] Isaiah 50:10; 1 John 5:13; Psalm 88; Psalm 77:1-4, 7-10; Jonah 2:4
[2] Isaiah 54:7-10; Matthew 5:3-4; Psalm 31:22; Psalm 73:13, 22-23
[3] Philippians 3:8-9; Psalm 10:17; Psalm 42:1-2, 5, 11;
[4] 2 Timothy 2:19; Isaiah 50:10; Psalm 66:18-20
[5] Isaiah 40:11, 29, 31; Matthew 11:28, 12:20, 26:28
[6] Mark 9:24
[7] Acts 2:37, 16:30
[8] Romans 4:11; 1 Corinthians 11:28