It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: Whoever wishes to swear an oath, should swear only by Allah Almighty. Since the Quraysh used to swear by their forefathers, the Prophet (peace and blessings be upon him) said to them: Do not swear by your forefathers.

It is narrated from Sa'd bin Ubaidah, he says: I was in a gathering with Sayyiduna Abdullah bin Umar (may Allah be pleased with them), when he heard a man sitting in another gathering say: "No, by my father's oath," so he threw a pebble at him and said: Sayyiduna Umar (may Allah be pleased with him) used to swear in the same way, but the Noble Prophet (peace and blessings be upon him) said: This is shirk (associating partners with Allah).

(Second chain) There is a similar narration, except that in it: The Noble Prophet, peace and blessings be upon him, forbade this and said: Whoever swears by anything other than Allah Almighty has committed shirk. The words of one narrator are: And that is shirk.

It is narrated from Sayyiduna Umar (may Allah be pleased with him) that when he swore an oath saying, "No, by my father's oath," the Messenger of Allah (peace and blessings be upon him) said to him: "Stop! Indeed, whoever swears an oath by anything other than Allah has committed shirk."

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that when the Noble Prophet (peace and blessings be upon him) heard Sayyiduna Umar (may Allah be pleased with him) saying, "By my father," the Prophet (peace and blessings be upon him) said: "Indeed, Allah Almighty forbids you from swearing by your forefathers. When anyone swears an oath, let him swear by Allah Almighty, or remain silent." Sayyiduna Umar (may Allah be pleased with him) said: "After that, I never intentionally swore such an oath, nor even while quoting someone else."

A narration of the same kind is reported from Sayyiduna Umar (may Allah be pleased with him), except that in it, Sayyiduna Umar (may Allah be pleased with him) said: "By Allah, since I heard the Messenger of Allah (peace and blessings be upon him) forbidding it, I have neither taken such an oath nor spoken such words, neither intentionally nor while quoting someone else."

It is narrated from Sayyiduna Umar (may Allah be pleased with him), who says: I was with the Noble Prophet (peace and blessings be upon him) in a battle. I swore an oath saying: No, by my father! Then someone behind me called out loudly: Do not swear by your forefathers. When I looked, it was the Messenger of Allah (peace and blessings be upon him).

It is narrated from Sayyiduna Abdur Rahman bin Samurah (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: Do not swear by your forefathers and by Taghut. In his narration, Yazid (the narrator) mentioned the word "Tawaghi."

It is narrated from Sa’d bin Ubaidah, he says: I was sitting with Sayyiduna Abdullah bin Umar (may Allah be pleased with them), then I left a man from Kinda with Sayyiduna Ibn Umar (may Allah be pleased with him) and went to Sa’eed bin Musayyib. That Kinda man, in a state of anxiety, reached there. I said to him: Who is after you? He said: Just now a man came to Sayyiduna Abdullah bin Umar (may Allah be pleased with them) and he swore by the Ka’bah. He (Ibn Umar) said: Swear by the Lord of the Ka’bah, because Sayyiduna Umar (may Allah be pleased with him) used to swear by his father, but the Noble Prophet (peace and blessings be upon him) said to him: Do not swear by your father, because whoever swears by other than Allah has committed shirk (associating partners with Allah).

Qutaylah bint Saifi Juhaniyyah (may Allah be pleased with her) says: A Jewish scholar came to the Messenger of Allah (peace and blessings be upon him) and said: O Muhammad! You are the best of people, but if only you did not commit shirk? The Prophet (peace and blessings be upon him) said: Subhan Allah! (How astonishing!) How is that? He said: When you take an oath, you say: By the Ka'bah. The Prophet (peace and blessings be upon him) remained silent for a while and then said: This man has spoken a word, so now whoever takes an oath should swear by the Lord of the Ka'bah (and not by the Ka'bah itself). He then said: O Muhammad (peace and blessings be upon him)! You are very good people, but if only you did not set up equals with Allah! The Prophet (peace and blessings be upon him) said: Subhan Allah! How is that? He said: You say: Whatever Allah wills and you will. The Messenger of Allah (peace and blessings be upon him) remained silent for a while, then said: This man has spoken a word; if anyone says Masha Allah (whatever Allah wills), he should pause and then say: thumma shi'ta (and then you will).