Al-Hasan (al-Basri) narrates: Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) intended to forbid Hajj al-Tamattu', so Sayyiduna Ubayy (may Allah be pleased with him) said to him: You do not have the authority for that, because we performed Hajj al-Tamattu' with the Messenger of Allah. Sayyiduna Umar (may Allah be pleased with him) intended to forbid the garments (hullahs) of "al-Hirah", because they are dyed with urine. Sayyiduna Ubayy (may Allah be pleased with him) said to him: You do not have this authority, because the Prophet (peace and blessings be upon him) wore that cloth, and we too wore it in his time.
Imam Ahmad recorded it; the narrator al-Hasan did not hear from Sayyiduna Umar (may Allah be pleased with him) nor from Sayyiduna Ubayy (may Allah be pleased with him).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1576