Robert Traill (The Throne of Grace), Works 1:230:
There is no worse company in an evil day than an evil conscience. It is worse company than the devil’s. His company is that of a tempter and accuser; but an evil conscience is a judge condemning, and an executioner tormenting a man. Therefore herein exercise yourselves, to have a conscience void of offence toward God and toward men, Acts 24:16. It is usually seen, that times of great trials do dart in some light into men’s consciences, and do make men look into their hearts and ways more narrowly, and spy small faults that they could not see at other times; for they are days of darkness in one sense, and days of light in another. Study therefore to keep thy conscience clean and pure, by holy and tender walking, and by daily believing; for it is the blood of Christ that only can purge the conscience from dead works to serve the living God, Heb. 9:14.