Their guards also are such as are used in a kingly government, not a despotic one; for the guards of their kings are his citizens, but a tyrant’s are foreigners. The one commands, in the manner the law directs, those who willingly obey; the other, arbitrarily, those who consent not. The one, therefore, is guarded by the citizens, the other against them.

[οἱ γὰρ πολῖται φυλάττουσιν ὅπλοις τοὺς βασιλεῖς, τοὺς δὲ τυράννους ξενικόν: οἱ μὲν γὰρ κατὰ νόμον καὶ ἑκόντων οἱ δ᾽ ἀκόντων ἄρχουσιν, ὥσθ᾽ οἱ μὲν παρὰ τῶν πολιτῶν οἱ δ᾽ ἐπὶ τοὺς πολίτας ἔχουσι τὴν φυλακήν.]

Aristotle (384-322 BC) Greek philosopher
Politics [Πολιτικά], Book 3, ch. 14 [1285a25] [tr. Ellis (1776)]
    (Source)

Alt. trans.:

• "The guard of the king is, for the same cause, one that belongs to a monarch and not to a tyrant, for the citizens protect their kings with their arms; but it is aliens who guard despots. For the former rule legally over willing subjects, the latter over unwilling; so that the former are guarded by their subjects, the latter against them." [tr. Bolland (1877)]
• "Wherefore also their guards are such as a king and not such as a tyrant would employ, that is to say, they are composed of citizens, whereas the guards of tyrants are mercenaries. For kings rule according to the law over voluntary subjects, but tyrants over involuntary; and the one are guarded by their fellow-citizens, the others are guarded against them." [tr. Jowett (1921)]
• "Also their bodyguard is of a royal and not a tyrannical type for the same reason; for kings are guarded by the citizens in arms, whereas tyrants have foreign guards, for kings rule in accordance with law and over willing subjects, but tyrants rule over unwilling subjects, owing to which kings take their guards from among the citizens but tyrants have them to guard against the citizens." [tr. Rackham (1944)]
• "For the same reason, their bodyguard is of a kingly rather than a tyrannical sort. For the citizens guard kings with their own arms, while a foreign element guards the tyrant, since the former rule willing persons in accordance wit the law, while the latter rule unwilling persons. So the ones have a bodyguard provided by the citizens, the other one that is directed against them." [tr. Lord (1984)]
• "And their bodyguards are kingly and not tyrannical due to the same cause. For citizens guard kings with thier weapons, whereas a foreign contingent guards tyrants. For kings rule in accord with the law and rule voluntary subjects, whereas the latter rule involuntary ones, so that the former have bodyguards drawn from the citizens, whereas the latter have bodyguards to protect them against the citizens." [tr. Reeve (2007)]
• "Citizens guard their kings with arms; foreigners protect tyrants. This is because kings rule according to the law and with willing citizens while tyrants rule the unwilling. As a result, kings have guards from their subjects and tyrants keep guards against them." [tr. @sentantiq]

Original Greek.