'Adversary' in the Bible

Then the guiding angel showed me Joshua the high priest [representing disobedient, sinful Israel] standing before the Angel of the Lord, and Satan standing at Joshua’s right hand to be his adversary and to accuse him.

For before those days there were no wages for man or animal; nor was there any peace or success for him who went out or came in because of his enemies, for I set all men against one another.