It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he asked Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) about a verse of the Book of Allah while the Prophet (peace and blessings of Allah be upon him) was delivering a sermon. Ubayy turned away from him and did not answer his question. When the prayer was completed, Ubayy bin Ka'b said to Abdullah bin Mas'ud (may Allah be pleased with him): "(Today) you have not performed Jumu'ah." (Hearing this) Abdullah bin Mas'ud (may Allah be pleased with him) asked the Messenger of Allah (peace and blessings of Allah be upon him), and he (peace and blessings of Allah be upon him) said: "Ubayy has spoken the truth."