It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that once the Noble Prophet (peace and blessings be upon him) heard Sayyiduna Umar (may Allah be pleased with him) swearing by his father. He said: "Allah Almighty forbids you from swearing by the names of your forefathers. Therefore, when any one of you wants to swear an oath, let him swear by the name of Allah, otherwise let him remain silent." Sayyiduna Umar (may Allah be pleased with him) says: "After that, I never swore such an oath intentionally or even while quoting someone."