183. Rabbi Aba was before Rabbi Shimon. He said to him: It is written, "And you shall put in the breastplate of Judgment the Urim and the Tumim" (Shemot 28:30). We learned that Urim (Eng. 'lights') MEANS that they illuminated that which was required, NAMELY WHATEVER WAS ASKED. Tumim (Eng. 'complete') means that they fulfilled what was said. BUT THIS EXPLANATION IS NOT ENOUGH, we need to know more.
184. He said to him: Surely it is so. Thus, the breastplate and the Efod correspond to Urim and Tumim. This is a secret of Tefilin and the knot of Tefilin, that correspond to these two. He opened the discussion and said: "And you shall see My back, but My face shall not be seen" (Shemot 33:23). "And you shall see My back"; we learned that the Holy One, blessed be He showed Moses the knot of Tefilin. "My face" are the Tefilin themselves. HE EXPLAINS: "My face" are Tefilin, the high secret, the Holy Name. "My back," is the secret of the knot of Tefilin. It is known among the friends that TEFILIN are the shining mirror, WHICH IS ZEIR ANPIN, and this, THE KNOT OF TEFILIN, is the mirror which does not shine, WHICH IS MALCHUT.
185. Correspondingly, these are Urim for they shine (Heb. meirim) with their utterances, NAMELY, ZEIR ANPIN, THE SHINING MIRROR. And these are Tumim so called for completing with their utterances, NAMELY MALCHUT, SHINING BY THE ILLUMINATION OF CHOCHMAH IN THE SECRET OF "AND YOU SHALL SEE MY BACK," WHERE ALL PERFECTION LIES. URIM ARE the face, and TUMIM ARE the back. This is the secret of sound and speech. Sound, WHICH IS ZEIR ANPIN shines upon the speech, WHICH IS MALCHUT, so it may speak. For the speech completes the word, NAMELY, THE VOICE IS THE MAIN AND SUBSTANTIAL PART, AND THE SPEECH COMPLETES IT. They always rise together, and never separate, FOR YOU CAN NEVER SEPARATE SOUND AND SPEECH. Hence, the breastplate and the Efod, the one is the face and the other the back, and all pertain to the same principle with no separation whatsoever, LIKE SOUND AND SPEECH.
268. It is written, "And you shall put in the breastplate of judgment the Urim and the Tumim" (Shemot 28:30). It was explained that the MEANING OF Urim (Eng. 'lights') is that they illuminate, in the secret of the shining mirror, NAMELY, ZEIR ANPIN, and this is the engravings of the letters of the Holy Name in the secret of 42, with which the worlds were created. The letters were sunken into it. "The Tumim" refer to the secret of the letters contained in the mirror which does not shine, WHICH IS MALCHUT, shining with the 72 engraved letters, in the secret of the Holy Name. THE NAME OF SEVENTY-TWO IS THE SECRET OF REVEALING THE LIGHT OF CHOCHMAH THAT IS WITHIN MALCHUT. Together they are called 'Urim and Tumim'.