Tibi istum ad munimentum mei committo, si recte agam; sin aliter, in me magis.

One day as Trajan was putting a captain of the guards (or a prætorian prefect) in possession of his post, he gave him a drawn sword or dagger, according to the custom, and spoke thus. Related by Aurelius Victor, De Caesaribus Aurelii Victoris Historiae Abbreviatae, sec 13. Also by Cassius Dio. Reported in S. A. Bent (ed.) Familiar Short Sayings of Great Men, 9th ed. (1896) p. 614