Jeremiah 50:20:

“In those days and in that time, declares the LORD, iniquity shall be sought in Israel, and there shall be none, and sin in Judah, and none shall be found, for I will pardon those whom I leave as a remnant.”

What it is really saying is not that Israel will be free from iniquity or that Judah will be altogether sinless, but that the guilt of their iniquity and sin will be absolved and paid for by Christ.

But I really love the phrasing which is present in most translations.

Iniquity and sin shall be sought for, but none shall be found because God has pardoned the remnant. For me this serves as a reminded that God’s pardoning work through Christ is the first and most important element in our sanctification.

God’s pardon produces sanctification, never the other way around.