It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that indeed the Messenger of Allah (peace and blessings be upon him) found Umar (may Allah be pleased with him) while he was swearing by his father. So the Prophet (peace and blessings be upon him) said: "Indeed, Allah forbids you from swearing by your forefathers. So whoever wants to swear an oath, let him swear by Allah or remain silent."