Charles Ellicott Commentary Zechariah 13:9

"And I will bring the third part into the fire, and will refine them as silver is refined, and will try them as gold is tried. They shall call on my name, and I will hear them: I will say, It is my people; and they shall say, Jehovah is my God." — Zechariah 13:9 (ASV)

The third part. —Amidst all the calamities that would overtake the land, a remnant would be saved and purified. In the light of the Gospel we may (if we retain them in their present context) understand these words as fulfilled in those who embraced Christianity; but the prophet, from the Old Testament standpoint, speaks vaguely, and following the analogy of the past captivity (Isaiah 6:13).