Sahih Bukhari | Volume 8 | Hadith Number 642
Narrated by Ibn 'Umar
I heard 'Umar saying, "Allah's Apostle said to me, 'Allah forbids you to swear by your fathers.'" 'Umar said, "By Allah! Since I heard that from the Prophet, I have not taken such an oath, neither intentionally, nor by reporting the oath of someone else."