Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: The Prophet Muhammad (peace and blessings be upon him) saw Sayyiduna Umar bin Khattab (may Allah be pleased with him) swearing an oath by his father's name, so he said: Indeed, Allah Almighty has forbidden you from swearing by your forefathers' names. Whoever has to swear an oath should swear by the name of Allah, otherwise he should remain silent.