Is paying money as charity when slandering Muslims a legitimate solution to get rid of sin, or is it a worldly desire that brings no reward?

Backbiting is forbidden by the Qur’an, Sunnah, and scholarly consensus. If a person commits to giving charity verbally when they backbite, it is a vow of obstinacy (nadhr lajaj). However, if it is not verbal, nothing is incumbent upon them. A Muslim should be deterred from committing sins by the fear of Allah’s punishment, not by a vow. Sheikh Muhammad ibn Salih al-Uthaymeen advised against making a vow the primary motivator for abandoning sin, because one might become accustomed to it. If one vows not to commit a sin but then does so, they must seek Allah’s forgiveness, repent, and offer an expiation for breaking an oath.