I read a story over shabbas from Tales of Tzaddikim, Bamidbar pg 251-252, Published by Mesorah Publications, and it quoted it from Sefer Chassidim, Siman 6407. I opened up my Sefer Chassidim and the last entry in it is 1172 (like this one, for example).
The basics to the story is of a man wanting to do teshuva and goes before a Tzaddik to ask how. The Rebbe tells him it is simple, all he has to do is never tell a lie. As a result, every time he wanted to do something wrong, he would say to himself, what will i say to someone who asks me about what I have done, thus, stopping himself from doing something wrong.
Is there another Sefer Chassidim or another way that it was organized? Is there another source for this story?