Musnad Ahmad 1012:28

Yazid narrated to us, Yahya—meaning Ibn Sa'id—informed us, from Muhammad ibn Yahya ibn Habban, that Ibn Muhayriz al-Qurashi, then al-Jumahi, informed him—and he was in the Levant and had met Mu'awiyah—that he informed him that al-Makhdaji, a man from Banu Kinanah, informed him that a man from the Ansar who was in the Levant, whose kunya was Abu Muhammad, informed him that the Witr prayer is obligatory. Al-Makhdaji mentioned that he went to 'Ubadah ibn al-Samit and mentioned to him that Abu Muhammad says: "The Witr prayer is obligatory." 'Ubadah ibn al-Samit said: "Abu Muhammad has lied. I heard the Messenger of Allah (ﷺ) say: 'Five prayers which Allah has prescribed upon the servants. Whoever performs them, not losing anything from them out of disregard for their right, has a covenant with Allah that He will admit him into Paradise. And whoever does not perform them has no covenant with Allah; if He wills, He will punish him, and if He wills, He will forgive him.'"