obey   disobey   order   command   bow     I am your king. You must obey me!     I command you to bow!     You can't disobey a direct order.

refuse   serve   betray   kneel - knelt     My slaves serve me well.     They refused to serve him.     The knight knelt before the king.

When a clause follows an order, suggestion, or hope, it's verb should be in the present tense.