The cross is pointed to here.
V.2-4 As a result of the cross, all Israel is going to be cleansed. Every unbeliever in the land will be destroyed (Matt. 25:31-46).
V.6 Those Israelites who have not known about the cross, will ask this question.
V.7 God proclaims Jesus Christ as His Fellow (companion), but His sword went into Him! The nation was scattered, while the believing remnant was blessed (Matt. 26:31).
V.8-9 Judah will be individually sifted. Two thirds of them will be unbelievers.