It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that Sayyiduna Umar (may Allah be pleased with him) said (in the course of speaking): "No, by my father!" So the Messenger of Allah (peace and blessings be upon him) said: "Do not swear by your fathers. Whoever swears by anything other than Allah has committed shirk."

It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that Sayyiduna Umar (may Allah be pleased with him) used to swear saying "By my father", so the Prophet (peace and blessings be upon him) forbade him and said: "Whoever swears by anything other than Allah has committed shirk", or he said: "It is shirk."

It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "Whoever swears by other than Allah has committed kufr (disbelief)." This hadith is sahih on the condition of the two Shaykhs, but they did not record it with this wording. I placed it in the Book of Faith (Kitab al-Iman) because of the word 'shirk' in it; and in the hadith of Mus'ab bin al-Miqdam from Isra'il it reads: "has committed kufr." As for the two Shaykhs, they recorded it only from the hadith of Salim, Nafi' and Abdullah bin Dinar from Ibn Umar, that the Prophet (peace and blessings be upon him) said to Umar: "Indeed Allah forbids you from swearing by your fathers", and that is all; this narration is different from that one.