'Adversary' in the Bible

When you go to war in your land against the adversary who oppresses you, then you shall sound an alarm with the trumpets. Then you will be remembered before Yahweh your God, and you will be saved from your enemies.

God's anger was kindled because he went; and the angel of Yahweh placed himself in the way for an adversary against him. Now he was riding on his donkey, and his two servants were with him.

The angel of Yahweh said to him, "Why have you struck your donkey these three times? Behold, I have come forth as an adversary, because your way is perverse before me: