Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrated: A Jew came to the Prophet (peace and blessings be upon him) and said: "Your community would be an excellent community, were it not that they set up equals (with Allah)." The Prophet (peace and blessings be upon him) said: "How do they set up equals?" He said: "They say: 'Whatever Allah wills and you will.'" The narrator said: The Prophet (peace and blessings be upon him) said: "Say: 'then you will.'" He also said: "Your community would be an excellent community, were it not that they associate partners (with Allah)." He explained that they say: "By the right of so-and-so" and "By the life of so-and-so." The Prophet (peace and blessings be upon him) said: "Whoever must swear, let him swear only by Allah Almighty."
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains Ubayd bin al-Qasim, who is a liar and matruk (abandoned).