Robert Traill (The Throne of Grace), Works 1:187:
Eph. 6:16, “Above all, taking the shield of faith, wherewith ye shall be able to quench all the fiery darts of the devil.” They are darts, they are the devil’s darts, they are fiery darts, there is an all of them; yet by faith you may be able to quench them all. Why is so much said of faith? Because, as Christ’s strength is the believer’s strength, so faith is that only in a believer that acts on this strength, draws it in, and acts in it. Separate faith from its object, Christ, either in justification or in sanctification, and it becomes an imagination, a vanity, a nothing. Now, consider how cunningly Satan deals with believers, and how simply they are gulled by him in temptation. He persuades, and often prevails with them, to lay aside the shield of faith, when they should mainly use it. How foolish were that man that would yield his arms to an implacable enemy? Christ knew Peter’s danger, and provides graciously for it: I have prayed for thee, that thy faith fail not, Luke 22:32.
Source: https://www.puritanboard.com/threads/why-is-so-much-said-of-faith.90957/, Comment 1