The Book of Oaths (Kitab Al-Aiman)

Muslim :: Book 15 : Hadith 4040

Ibn 'Umar heard Allah's Messenger (may peace be upon him) as saying: He who has to take an oath, he must not take oath but by Allah. The Quraish used to take oath by their fathers. So he (the Holy Prophet) said: Do not take oath by your fathers.