Umar said, "The Messenger of Allah ﷺ said to me, 'Allah forbids you from swearing by your fathers.'"Umar continued, "By Allah, I have never sworn by them since I heard the Prophet ﷺ say this, neither on my own nor quoting another."
قال لي رسول الله ﷺ: إن الله ينهاكم أن تحلفوا بآبائكم قال عمر: فو الله ما حلفت بها منذ سمعت النبي ﷺ ذاكرا ولا أثرا.
Bukhari narrated it in the Book of Oaths and Vows (6647), and Muslim narrated it in the Book of Oaths and Vows (1:1646), both of them through the route of Yunus, from Ibn Shihab, from Salim bin Abdullah, from his father, who said, "I heard Umar bin Khattab," and he mentioned it.As for his saying "athira," Abu Ubayd said, it means "I did not attribute it to anyone else." That is, he says, I did not mention it as coming from anyone else.