יחזקאל לח:ז פירוש: רש״י

Be prepared and make ready for yourself Prepare yourself, and make ready for yourself an army of others.

be prepared [as translated,] be prepared.

and you will be to them for a guardian It is the custom of kings to pay attention, concerning their armies, to how they will march forth, and to appoint guards so that a destroyer should not come upon his army at night.