Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: The Prophet Muhammad (peace and blessings be upon him) said this: "Whoever has to take an oath should only swear by the name of Allah." The Quraysh used to swear by the names of their forefathers. The Prophet Muhammad (peace and blessings be upon him) said: "Do not swear by the names of your forefathers."