Objection 1. It would seem that use precedes command. For command is an act of the reason presupposing an act of the will, as stated above (Article 1). But, as we have already shown (16, 1), use is an act of the will. Therefore use precedes command.
Objection 2. Further, command is one of those things that are ordained to the end. But use is of those things that are ordained to the end. Therefore it seems that use precedes command.
Objection 3. Further, every act of a power moved by the will is called use; because the will uses the other powers, as stated above (Question 16, Article 1). But command is an act of the reason as moved by the will, as stated above (Article 1). Therefore command is a kind of use. Now the common precedes the proper. Therefore use precedes command.
On the contrary, Damascene says (De Fide Orth. ii, 22) that impulse to action precedes use. But impulse to operation is given by command. Therefore command precedes use.
I answer that, use of that which is directed to the end, in so far as it is in the reason referring this to the end, precedes choice, as stated above (Question 16, Article 4). Wherefore still more does it precede command. On the other hand, use of that which is directed to the end, in so far as it is subject to the executive power, follows command; because use in the user is united to the act of the thing used; for one does not use a stick before doing something with the stick. But command is not simultaneous with the act of the thing to which the command is given: for it naturally precedes its fulfilment, sometimes, indeed, by priority of time. Consequently it is evident that command precedes use.
Reply to Objection 1. Not every act of the will precedes this act of the reason which is command; but an act of the will precedes, viz. choice; and an act of the will follows, viz. use. Because after counsel's decision, which is reason's judgment, the will chooses; and after choice, the reason commands that power which has to do what was chosen; and then, last of all, someone's will begins to use, by executing the command of reason; sometimes it is another's will, when one commands another; sometimes the will of the one that commands, when he commands himself to do something.
Reply to Objection 2. Just as act ranks before power, so does the object rank before the act. Now the object of use is that which is directed to the end. Consequently, from the fact that command precedes, rather than that it follows use.
Reply to Objection 3. Just as the act of the will in using the reason for the purpose of command, precedes the command; so also we may say that this act whereby the will uses the reason, is preceded by a command of reason; since the acts of these powers react on one another.
Source: Summa Theologica (New Advent)