It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that once the Prophet Muhammad (peace and blessings be upon him) heard Sayyiduna Umar (may Allah be pleased with him) swearing by his father. He said: Allah 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.