'Adversary' in the Bible

“When you enter into battle in your land against an adversary who is attacking you, sound short blasts on the trumpets, and you will be remembered before the Lord your God and be delivered from your enemies.

And God's anger was kindled because he went: and the angel of the LORD stood in the way for an adversary against him. Now he was riding upon his ass, and his two servants were with him.

and the messenger of Jehovah saith unto him, 'Wherefore hast thou smitten thine ass these three times? lo, I -- I have come out for an adversary, for thy way hath been perverse before me,