Musnad Ahmad 27:737

Yahya narrated to us, from Ibn Abi Dhi'b, from al-Zuhri, from Salim, from his father: "That the Messenger of Allah (peace and blessings of Allah be upon him) combined the Maghrib and Isha prayers at Jam' (Muzdalifah) with one iqamah. He did not perform voluntary prayers (tasbih) between them, nor after either one of them."