출애굽기 28:15 해설: Rashi, Kli Yakar, Rashbam & Rabbeinu Bahya

חשן משפט THE BREAST-PLATE OF JUDGMENT — it was so called because it atoned for any error in judgment (cf. Zevachim 88b; Jerusalem Talmud Yoma 7:5). Another explanation of why it is called “the breast-plate of משפט”, is because it makes its statements clear (definite — so that there can be no doubt about their meaning) and its promise is true; discerement in old French, (sentence of judgment). Because the word משפט is used in three senses: the contentions of the parties to the law-suit, the pronouncement of the sentence and the punishment attendant on the sentence, whether it be punishment of death or punishment of flagellation or punishment involving a monetary payment; here it is used in the sense of making its statements definite, so that this is the breast-plate with the Urim and Thummim which explains and makes its statement clear.

And you shall make a breastplate of judgment, of skilled work. Throughout all the priestly garments, the term skilled work is mentioned only regarding the ephod and the breastplate. This indicates that this atonement is for a specific sin where the thought is considered equivalent to the action, which is found only in idolatry, as explained earlier in the section about the ephod. The breastplate comes to atone for corruption in judgment, as judicial matters are entrusted to the judge’s heart, for a judge has only what his eyes see, and it is in his power to declare right as left and left as right, depending on the situation, the person, the time, and the place. If a judge says, “This is how it appeared to me,” who can contradict him except God alone, who examines the hearts of men? Therefore, the breastplate was placed on Aaron’s heart, because judgments are entrusted to the heart, and thus it was of skilled work to atone for the judge’s thoughts.
Since it says skilled work like the work of the ephod, it links the concept of skilled work to the ephod, telling you that corruption in judgment is equivalent to idolatry, as our Sages said (Sanhedrin 7b): “Whoever appoints an unworthy judge is as if he planted an Asherah,” which refers to idolatry. Therefore, it says that the breastplate of judgment, which atones for judicial corruption, should be like the work of the ephod, which atones for idolatry. Similarly, our Sages interpreted the verse You shall not make with Me gods of silver as referring to an unworthy judge (Jerusalem Talmud, Bikkurim 3:3), because this sin primarily depends on the judge’s thoughts, as it is written (Proverbs 12:5): The thoughts of the righteous are just, for they are complete in judgment even in their thoughts.
It was square — because every judge needs to be complete in the four qualities listed in the verse And you shall choose (Exodus 18:21). It was doubled — because the sin is also doubled, as it harms one person financially and another spiritually by allowing him to keep another’s money unjustly. This is what the Midrash concludes (Lamentations Rabbah 1:57): “They sinned doubly and were punished doubly,” for they sinned through corruption of justice, as it says (Isaiah 1:21): Righteousness lodged in it, and they sinned through idolatry, which is also a double sin, as it says (Jeremiah 2:13): They have forsaken Me, the fountain of living waters, to hew out for themselves broken cisterns.
From all this, we learn the similarity between corruption in judgment and idolatry, which is why the breastplate was like the work of the ephod. A span its length — because corruption in judgment causes the destruction of the world, and its correction is like becoming a partner with the Holy One, blessed be He, in the work of Creation, about which it says and measured heaven with the span (Isaiah 40:12).

חשן משפט, the name reflects the fact that in the pocket of the breastplate there was placed the parchment with the Holy name of G’d, known popularly as urim vetumim, the tool by means of which G’d could be consulted if the High Priest did not know the answer to a question involving Jewish religious law. He would then consult G’d and receive his answer by the letters on the breastplate becoming illuminated. (compare Numbers 27,21).

כמעשה אפד AFTER THE WORK OF THE EPHOD — the work of an artist and of the five materials.