Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: Once the Prophet Muhammad (peace and blessings be upon him) found Sayyiduna Umar bin Khattab (may Allah be pleased with him) in a situation where he was walking among some riders and swearing by the name of his father. So the Prophet Muhammad (peace and blessings be upon him) said: Indeed, Allah Almighty has forbidden you from this matter, that you swear by the names of your forefathers. Whoever has to swear, let him swear by the name of Allah or remain silent.