See post #8
“And I will pour out on the house of David and the inhabitants of Jerusalem a spirit[a] of grace and supplication. They will look on[b] me, the one they have pierced, and they will mourn for him as one mourns for an only child, and grieve bitterly for him as one grieves for a firstborn son. .. “On that day a fountain will be opened to the house of David and the inhabitants of Jerusalem, to cleanse them from sin and impurity.”Zech 12;10-13:1
Here is their atonement, through the One pierced for them...
Here also- 5But he was wounded for our transgressions, he was bruised for our iniquities: the chastisement of our peace was upon him; and with his stripes we are healed.
6All we like sheep have gone astray; we have turned every one to his own way; and the LORD hath laid on him the iniquity of us all.
Isaiah 53;5-6