" 'Umar said: I swear by Allah, I never swore by it personally or reporting it from others."
Sunan Abi Dawud Book 22, Hadith 9
← Previous Hadith The Messenger of Allah (ﷺ) found 'Umar al-Khattab in a caravan while he was swearing by his father. So he said: Allah forbids you to swear by forefathers. If anyone swears, he must swear by Allah or keep silence.

Sunan Abi Dawud Book 22, Hadith 8 Next Hadith → Ibn Umar heard a man swearing: No, I swear by the Ka'bah. Ibn Umar said to him: I heard the Messenger of Allah (ﷺ) say: He who swears by anyone but Allah is polytheist.

Sunan Abi Dawud Book 22, Hadith 10