Ibrahim (may Allah have mercy on him) reports from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that he asked Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him), while the Prophet of Allah (peace and blessings be upon him) was delivering the sermon, about a verse of the Book of Allah, but he turned away from him and did not answer him. Then, when he had finished his prayer, he said: You have not (properly) attended the Jumu'ah prayer. Sayyiduna Ibn Mas'ud (may Allah be pleased with him) asked the Messenger of Allah (peace and blessings be upon him) (about this), and he (peace and blessings be upon him) said: "Ubayy has spoken the truth."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9507