"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
This is clearly a picture of Jesus. God is speaking here, and He says, "look on ME". Jesus is God! He is the one whom WE have pierced, the "only Son" (John 3:16) of God, the "firstborn of all creation" (Col 1:15). We weep because He died for us, because He was "pierced for our transgressions" (Isa 53:5a), because it was our sin that held Him there at that cross... because we know how much He loves us and how little we love Him...
"On that day there shall be a fountain opened... to cleanse them from sin and uncleaness." - Zechariah 13:1
That day has come on Apr 3, 33AD. And that day will come in final fulfillment when all Israel recognizes Jesus as the Messiah. Our sins ARE forgiven. "With his wounds we are healed" (Isa 53:5b). Christians, live like it, sin no more. Weep over your sin, weep over His grace. "Look on me" He says. Look, look at our bloodied savior, the crucified Lord, the risen Christ... Look at the cross. And NEVER for one moment take your eyes off it, off Him.
Non-Christians, repent and taste this free forgiveness, "taste and see that the LORD is good" (Psa 34:8)! Taste freedom (cf. Gal 5:1)!