Thank you for the interpretive question on Joshua 22:17, “Do they mean that the sin wasn’t forgiven them or what do they mean by not cleansed until this day (Joshua 22:17)?”
The context of 22:17 is settlement of the Twelve Tribes into the Promised Land. The broader text says this in the NIV, “When they went to Gilead—to Reuben, Gad and the half-tribe of Manasseh—they said to them: 16 “The whole assembly of the LORD says: ‘How could you break faith with the God of Israel like this? How could you turn away from the LORD and build yourselves an altar in rebellion against him now? 17 Was not the sin of Peor enough for us? Up to this very day we have not cleansed ourselves from that sin, even though a plague fell on the community of the LORD! 18 And are you now turning away from the LORD?
The 9 tribes bring up the rebellion and suggested seduction of idol worship and immorality when the Israelites were at Peor from Numbers 25:1–3. It was there that they built an altar and Baal, committing immorality.
The fear of the 9 tribes that this altar was a repeat of the sin at Peor. They thought that the 3 tribes were being an idolatrous altar and build some idol on it. The effects of that idolatry and immorality still linger among them. There were still some people still wish to have that wild lifestyle and to be free from the restrictions given by God.
The building of this altar may re-ignite their passions and waywardness. When someone has committed an immoral act, the lingering effect or the desire to feel that again still remains in that person. It is not forgotten. They couldn’t rid themselves of that passion. If given the same situation again, the Israelites would revert back to the actions at Peor.
It is like the experience that once someone tasted or see something, that taste or sight can’t be erased from one’s experience. It will either attract or repulse that person. Death may not detract people from that action. There will be those who will “die” to experience it. It’s like being “hooked” on something and one battles against that desire. They know it is not good for them, but still they want it.
Summary: God has forgiven them, but the people’s desire is only suppressed, not removed from them.
-Kingston