Command, order, bid, enjoin, direct, instruct, charge mean to issue orders to someone to give, get, or do something.
Command and order agree in stressing the idea of authority, command implying its more formal and official exercise and order, its more peremptory, sometimes even arbitrary, exercise; thus, a king, a military officer, the captain of a ship, commands; a landowner orders a trespasser off his premises; one is apt to resent being ordered, except by those who have a right to command. But order is used by a physician with no such connotation.
Bid in this sense is usually somewhat literary or informal; it usually implies an ordering or directing (often with a suggestion of peremptoriness) directly and by speech.
Enjoin, direct, and instruct are all less imperative than command or order, but they all connote expectation of obedience.
Enjoin adds to the idea of authority the implication of urging or warning; direct and instruct suggest especially business, official, or diplomatic relations, direct being perhaps the more mandatory, instruct the more formal, of the two.
Charge, chiefly a literary term, implies not only enjoining but the imposition of a task as a duty.