That the ruler should be pure in thought.
The ruler should always be pure in thought, inasmuch as no impurity ought to pollute him who has undertaken the office of wiping away the stains of pollution in the hearts of others also; for the hand that would cleanse from dirt must needs be clean, lest, being itself sordid with clinging mire, it soil whatever it touches all the more. For on this account it is said through the prophet, Be ye clean that bear the vessels of the Lord (Isa. 1:0, Isa. 52:11). For they bear the vessels of the Lord who undertake, on the surety of their own conversation, to conduct the souls of their neighbours to the eternal sanctuary. Let them therefore perceive within themselves how purified they ought to be who carry in the bosom of their own personal responsibility living vessels to the temple of eternity. Hence by the divine voice it is enjoined (Exod. xxviii. 15), that on the breast of Aaron the breastplate 1268 of judgment should be closely pressed by binding fillets; seeing that lax cogitations should by no means possess the priestly heart, but reason alone constrain it; nor should he cogitate anything indiscreet or unprofitable, who, constituted as he is for example to others, ought to shew in the gravity of his life what store of reason he carries in his breast. And on this breastplate it is further carefully prescribed that the names of the twelve patriarchs should be engraved. For to carry always the fathers registered on the breast is to think without intermission on the lives of the ancients. For the priest then walks blamelessly when he pores continually on the examples of the fathers that went before him, when he considers without cease the footsteps of the Saints, and keeps down unlawful thoughts, lest he advance the p. 10b foot of his conduct beyond the limit of order. And it is also well called the breastplate of judgment, because the ruler ought ever with subtle scrutiny to discern between good and evil, and studiously consider what things are suitable for what, and when and how; nor should he seek anything for himself, but esteem his neighbours good as his own advantage. Hence in the same place it is written, But thou shalt put in the breastplate of Aaron doctrine and truth 1269 , which shall be upon Aarons breast, when he goeth in before the Lord, and he shall bear the judgment of the children of Israel upon his breast in the sight of the Lord continually (Exod. 18.30). For the priests bearing the judgment of the children of Israel on his breast before the face of the Lord means his examining the causes of his subjects with regard only to the mind of the judge within, so that no admixture of humanity cleave to him in what he dispenses as standing in Gods stead, lest private vexation should exasperate the keenness of his censure. And while he shews himself zealous against the vices of others, let him get rid of his own lest either latent grudge vitiate the calmness of his judgment, or headlong anger disturb it. But when the terror of Him who presides over all things is considered (that is to say of the judge within), not without great fear may subjects be governed. And such fear indeed purges, while it humiliates, the mind of the ruler, guarding it against being either lifted up by presumption of spirit, or defiled by delight of the flesh, or obscured by importunity of dusty thought through lust for earthly things. These things, however, cannot but knock at the rulers mind: but it is necessary to make haste to overcome them by resistance, lest the vice which tempts by suggestion should subdue by the softness of delight, and, this being tardily expelled from the mind, should slay with the sword of consent.
For breastplate (A.V.) the LXX. has λογεῖον, and the Vulgate, from which St. Gregory quotes, rationale. On the significance of this word the application depends. Anciently an ornament called the rationale was attached to the vestments of bishops. “Rationale…Ornamenti genus quo ornantur casulæ aliaque vestes ecclesiasticæ” (Ducange). The vestment itself seems also to have been sometimes called the rationale. “Vestis episcopalis novæ legis, le pallium” (Ib.).10b:1269
For Urim and Thummim (as in A.V., retaining the Hebrew words), the LXX. has τὴν δήλωσιν καὶ τὴν ἀλήθειαν, and the Vulgate, quoted by St. Gregory, Doctrinam et Veritatem.