Reference for Moed Katan 36:22
ולא אמרן אלא דלא הדר נבט אבל הדר נבט לא ולא אמרן אלא דלית ליה אויבים אבל אית ליה אויבים אויבים הוא דאפקוה לקלא:
And how long would a persistent rumor be? - Said Abaye.' Nanna' told me, Local gossip lasts a day and a half; and that holds good only if it did not cease in the meantime, but if it had ceased in the meantime, we take no notice of it. If, however, it does cease in the meantime, the rule is [to disregard it] only where it was not [stopped] out of fear, but if it was stopped out of fear, it is not [to be disregarded]; again, the rule is [to disregard it] only where it does not break out again, but where it breaks out again [we do] not [disregard it]; also, the rule is [to disregard it] when he [the maligned] person has no enemies, but if he has enemies, [we say] it is his enemies who have spread the [adverse] rumor.