“Humble yourselves, therefore, under the mighty hand of God so that at the proper time He may exalt you, casting all your anxieties on Him because He cares for you. Be sober-minded; be watchful. Your adversary the devil prowls around like a roaring lion, seeking someone to devour. Resist him, firm in your faith…” — 1 Peter 5:6-9
What does it mean for Satan to “devour” a Christian like a ravenous lion? Well, Peter’s call to resist him “firm in your faith,” implies that the devouring imagined here is one that consumes faith. For someone to be so devoured would mean that faith crumbles, that faith gives way, that—like Peter himself on the night of Christ’s betrayal—faith falls before the fearful onslaught of this diabolical lion. This is the devouring that Peter—now reinstated by resurrecting grace—warns his readers against.
In this picture, then, Satan roars in the background like a lion intent on devouring the wayward believer. However, the saint is pictured as resisting the devil’s assaults “firm in his faith”. Notice that this resistance is not some brazen spiritual warfare, but rather is a child-like, desperate dependence on the crucified and risen Jesus Christ. As we humble ourselves under (or, in this case, “within”) the mighty hand of God—receiving what difficulties God’s sovereign wisdom ordains and casting the cares stirred up by those difficulties back onto the heart of love that decreed them for our good—we are resisting Satan firm in our faith.
See also that the hand of Christ (representing both His person and the work of His death, resurrection, and present reign) not only hides the Christian as a sure refuge, but also holds the bit and bridle in Satan’s mouth. Yes, the devil is an enemy, yes, he is opposed to God and to his people and has power to destroy the body, but he is—at every step—bound by the leash of God’s sovereign will….and for the one trusting in Jesus Christ, that will is only, ever, and always good.
[Explanation continued in the comments]