'Adversary' in the Bible

When you go to war in your land against the adversary who attacks you, then you shall sound an alarm with the trumpets, that you may be remembered before the Lord your God, and be saved from your enemies.

But God was angry because he was going, and the angel of the Lord took his stand in the way as an adversary against him. Now he was riding on his donkey and his two servants were with him.

The angel of the Lord said to him, “Why have you struck your donkey these three times? Behold, I have come out as an adversary, because your way was contrary to me.