"No, by the Kaabah."Ibn Umar said to him, "I heard the Messenger of Allah ﷺ say, 'Whoever swears by anything other than Allah has committed shirk.'"
لا والكعبة. فقال له ابن عمر: إني سمعت رسول الله ﷺ يقول: من حلف بغير الله فقد أشرك.
Narrated by Abu Dawud (3251), Tirmidhi (1535), and Ahmad (5256, 5222), and Ibn Hibban graded it sahih (4358), as did Hakim (4/297), and Bayhaqi (10/29), all of them through various routes from Hasan bin Ubaydullah Nakhai, from Saad bin Ubayda, who said, "I was with Ibn Umar when a man swore an oath by the Kaaba..." and so on. Tirmidhi said, "A hasan hadith." Hakim said, "Sahih according to the criteria of the two Shaykhs [Bukhari and Muslim]."I say, Hasan bin Ubaydullah is among the narrators used by Muslim alone, and its chain is sahih, but Bayhaqi said, "This is something that Saad bin Ubayda did not hear directly from Ibn Umar." This is based on what was narrated from Saad bin Ubayda, who said, "Muhammad Kindi and I sat with Abdullah bin Umar, then I got up and left him and sat with Saeed bin Musayab." He said, "Then my companion came, his face pale and his color changed, and he said, 'Get up and come with me.' I said, 'Wasn't I just sitting with you a moment ago?' Saeed said, 'Go to your companion.'" He said, "So I went to him, and he said, 'Did you not hear what Ibn Umar said?' I said, 'What did he say?' He said, 'A man came to him and said, "O Abu Abdul-Rahman, is it wrong for me to swear by the Kaaba?" He said, "Why would you swear by the Kaaba? If you swear by the Kaaba, then swear by the Lord of the Kaaba. Umar used to say when he swore, 'No, by my father,' and one day he swore by it in the presence of the Messenger of Allah ﷺ, so the Messenger of Allah ﷺ said, "Do not swear by your father, nor by anything other than Allah, for whoever swears by other than Allah has committed shirk."'"'"This narration contains an unidentified man. Imam Ahmad (5375) narrated it from Husayn bin Muhammad, who said, Shayban told us, from Mansur, from Saad bin Ubayda, who said, and then recounted it, and this Muhammad Kindi is unidentified.I say, Saad bin Ubayda is among the trustworthy narrators who relates the story directly from Ibn Umar himself without an intermediary. If this intermediary report is confirmed, then perhaps he later went back and heard it directly from Ibn Umar without an intermediary, since Amash and others have also narrated from him. Mansur is alone in narrating it from Saad bin Ubayda with an intermediary, and although Mansur is given precedence over Amash, Amash is supported by others.Tirmidhi said, "Some scholars have explained this hadith, saying that the phrase 'has disbelieved' or 'has committed shirk' is meant as a severe warning. The evidence for this is the hadith of Ibn Umar, that the Prophet ﷺ heard Umar saying, 'By my father, by my father,' and said, "Indeed, Allah forbids you from swearing by your fathers." And the hadith of Abu Hurairah, from the Prophet ﷺ, that he said, "Whoever says in his oath, 'By Lat and Uzza,' let him say, 'There is no god but Allah.'" This is similar to what has been narrated from the Prophet ﷺ that he said, "Indeed, showing off is shirk." Some scholars have explained this verse, "So whoever hopes for the meeting with his Lord, let him do righteous deeds" [Kahf 18:110], saying that it means, let him not show off." End of his statement.