For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh: How much more shall the blood of Christ, who through the eternal Spirit offered Himself without spot to God, purge your conscience from dead works to serve the living God? – Heb 9:13-14
Beloved, you and I know what it is, at times, to have defilement upon the conscience and to go mourning because we have erred from the Lord’s commands. The ungodly do not thus sorrow—their conscience, by fits and starts, accuses them, but they never listen to its accusations so as to feel their inability to draw near to God. No, they will even go with a guilty conscience to their knees and pretend to offer to God the sacrifice of prayer and praise while they are unforgiven, alienated and rebellious! You and I, if we are, indeed, the Lord’s people, cannot do this! Guilt on our conscience is to us a horrible thing. There are no pains of body—there are no tortures inflicted by the Inquisition which are at all comparable to the whips of burning wire which lash the guilty conscience! It is an awful thing to feel yourself guilty. And the better a man you are, the more will it grieve you to be consciously in a wrong state. We can come to God as sinners to seek pardon, but we cannot come before the Lord as dear children while there is any quarrel between us and our great Father. No, we must be clean, or we cannot approach our God! See how the priests washed their feet at the laver before they offered incense unto the Lord. We cannot have fellowship with God while there is a sense of unconfessed and unforgiven sin upon us…Sin on the conscience is a natural wall between God and the soul. You cannot get into loving communion until the conscience is at ease! Therefore, I charge you, fly at once to Jesus for peace! ~ C.H. Spurgeon
https://www.blueletterbible.org/comm/spurgeon_charles/sermons/1481.cfm