“And I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and pleas for mercy, so that, when they look on me, on him whom they have pierced, they shall mourn for him, as one mourns for an only child, and weep bitterly over him, as one weeps over a firstborn. (Zechariah 12:10 ESV)
Zechariah writes of the future from his perspective, about the day Jesus comes, the day of judgment for Jerusalem, and the salvation of those who are the true Israel. Jesus was pierced on the cross and this reference is clearly speaking of him as John indicates in his gospel (19:37). The passage before speaks of a siege upon Jerusalem which is a judgment upon Judah too (v. 2), likely a foreshadowing of the destruction of Jerusalem that occurred in 70AD. Jesus spoke about that day too (Mt 24-25). Judgment was coming in a terrible way upon Jerusalem for their rejection of the Lord. The events leading up to the destruction of the temple were horrifying to read which you can find in Josephus’ book, Jewish Wars). But before that happens, the spirit of grace and pleas for mercy will go forth, and they were in the preaching of the gospel, particularly by Peter at Pentecost in Acts 2. Peter explains that they (his audience) were the ones that crucified the Christ and the people are cut to the heart. Peter instructs them to repent and believe and they do. These form the church, the true Israel, who survive the judgment upon Jerusalem, though not all survive the persecution of the Romans that would later come.
The key is to understand that God’s judgment is real and it is terrible. The only way to escape it is to repent and believe in the gospel, to look upon the one that was pierced as a sacrifice for you and to give your life wholly to the Lord.
McCheyne’s reading plan: 2 Ch 30, Re 16, Zech 12, Ps 143