Charles Spurgeon Commentary Zechariah 13:1

"In that day there shall be a fountain opened to the house of David and to the inhabitants of Jerusalem, for sin and for uncleanness." — Zechariah 13:1 (ASV)

They will see that pardon when they have truly seen their sin.

Once the foulness of their transgression is perceived, then the fountain, the cleansing of sin, will be perceived too. No one ever knows the preciousness of the God-given remedy until he has felt the force of the terrible disease. No one by faith plunges into the crystal fountain of perfect cleansing without first lamenting the filthiness which needs to be removed.