Explainer / Tanakh
Zechariah 12:10
And I will pour upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace and of supplication; and they shall look to me whom they have pierced; and they shall mourn for him, as one mourns for his only son, and shall be in bitterness for him, as one who is in bitterness for his firstborn.
וְהִבִּיטוּ אֵלַי אֵת אֲשֶׁר־דָּקָרוּ וְסָפְדוּ עָלָיו כְּמִסְפֵּד עַל־הַיָּחִיד
We kept the ASV's wording, in modern English: "they shall look to me whom they have pierced; and they shall mourn for him."
Why
The speaker
is Yehovah (12:1, 12:4), so "I" and "me" in the verse are his.
אֵלַי, "to me."
This is the reading of the Masoretic text.
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Some Hebrew manuscripts read אֵלָיו, "to him."
אֵת אֲשֶׁר
אֵת marks the object and אֲשֶׁר is "whom" or "which." Together they can mean "the one whom" or "concerning the one whom." The ASV's "whom" gives the first.
The change of person
The verse moves from "to me" to "they shall mourn for him" (עָלָיו).
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The English keeps both persons as the Hebrew has them.
הַיָּחִיד, "only son."
The word is used of Isaac in Gen 22:2.
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The parallel line has "firstborn."
The quotation in John
John 19:37 quotes the verse in the third person: "They shall look on him whom they pierced." Rev 1:7 uses the same words.
"they shall look unto me whom they have pierced" (ASV); "they will look to me concerning the one they pierced, and mourn for him" (JPS-style).