Rashi on Tetzaveh 28:30

English: את האורים ואת התמים THE URIM AND THE THUMMIM — This was an inscription of the Proper Name of God which was placed between the folds (i. e. the two pieces forming the front and back) of the breast-plate through which it (the breast-plate) made its statements clear (lit., illuminated its words; מאיר from אור, light, this being an allusion to the אורים) and its promises true (מתמם from the root תמם, an allusion to תמים) (Yoma 73b). In the second Temple there was certainly the breast-plate (although other objects employed in the Temple Service were missing) for it was impossible that the High Priest should have lacked a garment, but that Divine Name was not within it. It was on account of the in