Tafsiran Keluaran 28:9: Da'at Zekenim, Kli Yakar, Or HaChaim & Rav Hirsch

ופתחת עליהם, “you are to engrave upon them;” in verse 21 of the same chapter we read: והאבנים תהיין על שמות בני ישראל, “and the stones (jewels) shall be according to the names of tribes of the Childern of Israel;” if that translation were correct we would face a contradiction. According to the first verse the letters would be engraved in the jewels, whereas according to the second verse the letters would protrude from the jewels. We must therefore assume that the Torah speaks once of how they appeared to the onlooker from the outside or from the inside, respectively.

And take two onyx stones. To atone for the two stone tablets that were broken, whereupon the bond was severed between these four: the Holy One, blessed be He, the tablets, Moses, and Israel. Through this atonement, all were reconnected, for the two onyx stones correspond to the two stone tablets. Shoham [onyx] was explained by Rabbeinu Bachya as containing the letters of “HaShem” [God’s name], and it also contains the letters of “Moshe” [Moses], and engraved upon it were all the names of the children of Israel. Thus, all four are now brought together to one inn, whereas initially they had forgotten their savior and consequently, God also forgot them. Now, after the atonement when they returned and remembered that God was their rock, they too would be on His two shoulders for remembrance.

ולקחת את שתי אבני שהם, "You are to take the two Shoham-stones, etc." The word את in this connection needs explaining. Perhaps the expression is to draw our attention to the previously mentioned Shoham-stones at the beginning of Parshat Terumah (25,7). The meaning of our verse then would be: "you shall take the two Shoham-stones which I have already commanded you to bring (as gifts)." This would account for the מתג, hyphen, between the words אבני and שהם, i.e. why only these two gemstones have been singled out here by name. These two stones performed a function additional to that of the gemstones called אבני מלואים, "stones to be set" (where the Torah did not employ the hyphen).