Hilchos Rechilus, chapter 5, section 7
To repent for the sin of believing rechilus, one must cease believing what one heard. If it is
difficult to think that the speaker made up the whole story, one must consider that perhaps he
added something to what the person said or did that put it in a negative light. One must decide
to not believe rechilus or lashon hara again and confess one’s sin. If one already repeated the
rechilus it to others, see earlier in hilchos lashon hara end of p. 64, and earlier in rechilus p. 24.