An enemy that contends with or resists; an antagonist or opponent. The Hebrew word for “adversary” (tsar) comes from a root meaning “harass; show hostility to.” (Nu 25:18; Ps 129:1) The Greek word an·tiʹdi·kos primarily refers to an “adversary at law” in a legal case (Lu 12:58; 18:3), but it can refer to others who are adversaries, or enemies, as in 1 Peter 5:8.

The most wicked Adversary, Satan the Devil, caused men and angels (see DEMON) to join his opposition to God and man. Satan first showed his opposition in the garden of Eden, where, through cruel and underhanded action, he led Eve and then Adam into a course of rebellion that brought sin and death upon all mankind. In the courts of heaven Satan displayed his antagonism, charging Jehovah with bribing Job for his loyalty, a charge which became an issue of universal importance.​—Job 1:6-11; 2:1-5; see SATAN.

Worshipers of Jehovah in all ages have endured similar opposition from the Adversary by means of his agents. For example, when the remnant of God’s people returned from Babylon, there were those who tried to prevent rebuilding the temple and the city wall. (Ezr 4:1; Ne 4:11) Hateful Haman, having the spirit of the Devil, proved to be a wicked adversary of the Jews in the days of Queen Esther. (Es 7:6) Christians today must be alert, watchful, on guard, and must put up a hard fight for the faith against the Adversary’s machinations. (Eph 6:11, 12; Jude 3) Peter counsels: “Keep your senses, be watchful. Your adversary, the Devil, walks about like a roaring lion, seeking to devour someone. But take your stand against him, solid in the faith.” (1Pe 5:8, 9) Eventually Jehovah’s power will triumph over all opposers.​—Jer 30:16; Mic 5:9.

When God’s people were unfaithful he allowed their adversaries to plunder and defeat them. (Ps 89:42; La 1:5, 7, 10, 17; 2:17; 4:12) The enemy, however, drew wrong conclusions from these victories, taking credit for themselves and praising their gods or feeling that they would not be called to account for the way they treated Jehovah’s people. (De 32:27; Jer 50:7) Jehovah was therefore obliged to humble these proud and boasting adversaries (Isa 1:24; 26:11; 59:18; Na 1:2); and this he did for his holy name’s sake.​—Isa 64:2; Eze 36:21-24.