1 Peter 5:8

Here the apostle does three things: - I. He shows them their danger from an enemy more cruel and restless than even the worst of men, whom he describes, 1. By his characters and names. (1.) He is an adversary: "That adversary of yours; not a common adversary, but an enemy that impleads you, and litigates against you in your grand depending cause, and aims at your very souls." (2.) The devil, the grand accuser of all the brethren; this title is derived from a word which signifies to strike through, or to stab. He would strike malignity into our natures and poison into our souls. If he could have struck these people with passion and murmuring in their sufferings, perhaps he might have drawn them to apostasy and ruin. (3.) He is a roaring lion, hungry, fierce, strong, and cruel, the fierce and greedy pursuer of souls. 2. By his business: He walks about, seeking whom he may devour; his whole design is to devour and destroy souls. To this end he is unwearied and restless in his malicious endeavours; for he always, night and day, goes about studying and contriving whom he may ensnare to their eternal ruin. II. Hence he infers that it is their duty, 1. To be sober, and to govern both the outward and the inward man by the rules of temperance, modesty, and mortification. 2.

— Matthew Henry's Concise Commentary (public domain)

Peter has in mind Christ's warning to himself to watch against Satan, from forgetting which he fell. Be sober . . . vigilant--"Care," that is, anxiety, will intoxicate the soul; therefore be sober, that is, self-restrained. Yet, lest this freedom from care should lead any to false security, he adds, "Be vigilant" against "your adversary." Let this be your "care." God provides, therefore do not be anxious. The devil seeks, therefore watch [BENGEL]. because--omitted in the oldest manuscripts The broken and disjointed sentences are more fervid and forcible. LUCIFER OF CAGLIARI reads as English Version. adversary--literally, "opponent in a court of justice" (Zac 3:1). "Satan" means opponent. "Devil," accuser or slanderer (Rev 12:10). "The enemy" (Mat 13:39). "A murderer from the beginning" (Joh 8:44). He counteracts the Gospel and its agents. "The tempter." roaring lion--implying his violent and insatiable thirst for prey as a hungry lion. Through man's sin he got God's justice on his side against us; but Christ, our Advocate, by fulfilling all the demands of justice for us, has made our redemption altogether consistent with justice. walketh about-- (Job 1:7; Job 2:2). So the children of the wicked one cannot rest. Evil spirits are in Pe2 2:4; Jde 1:6, said to be already in chains of darkness and in hell.

— Jamieson-Fausset-Brown Commentary (public domain)