The excellency of holy courage in evil times by Jeremiah Burroughs

4. Faith must be set on work when any difficult service is to be done, for the purifying of the heart, though you believe God will be with you, and strengthen you in the work, yet unless you make use of Faith to purify the heart, as well as believe, you may miscarry in the work, if there be any lust that lies next the heart, you will never be able for to do great things; for sin as it is of a defiling nature, so it is of a weakening nature. If you would have a spirit of power, you must have a sound mind. In Nehemiah, 13.3. When they were about a great work they separated the mixed company, & when you are about any great work, Exercise Faith to purge your hearts from corruption, Says David, Psal. 18.32. It is God that girdeth me with strength, and makes my way perfect. The girding of him with strength and making his way perfect went together: therefore: labour that the way with God in your own hearts may be perfect, and clean, and then God will gird you with strength.

4. Faith must be set on work when any difficult service is to be done, for the purifying of the heart, though you beleeve God will be with you, and strengthen you in the work, yet unless you make use of Faith to purifie the heart, as well as beleeve, you may miscarry in the work, if there be any lust that lies next the heart, you wil never be able for to do great things; for sin as it is of a defiling nature, so it is of a weakning nature. If you would have a spirit of power, you must have a sound mind. In Nehemiah, 13.3. When they were about a great work they separated the mixt company, & when you are about any great work, Exercise Faith to purge your hearts from corruption, Saies David, Psal. 18.32. It is God that girdeth me with strength, and makes my way perfect. The girding of him with strength and making his way perfect went together: therefore: labor that the way with God in your own hearts may be perfect, and clean, and then God will gird you with strength.