On the authority of Abu Muhammad al Hasan the son of 'Ali, the grandson of 'Ali said:
I memorized from the Messenger of Allah (may the blessings and peace of Allah be upon him):
Leave that which makes you doubt for that which does not make you doubt.
It was related by at-Tirmidhi and al-Nasa'i, at-Tirmidhi said that it was good and sound Hadith.