Gregory the Great, on Exod 28:30

“And thou shalt put in the rational of judgment doctrine and truth, which shall be on Aaron’s breast, when he shall go in before the Lord: and he shall bear the judgment of the children of Israel on his breast, in the sight of the Lord always.”

“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 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. Hence in the same place it is written, "But thou shall put in the breastplate of Aaron doctrine and truth, which shall be upon Aaron's 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." For the priest's 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 God's 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.”

Imported from an open dataset — not yet checked against the printed edition.