Zirr bin Hubaysh narrates that he stayed in the company of Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) and Sayyiduna Abd al-Rahman bin Awf (may Allah be pleased with him). Zirr stated that when the sun had set, both of them would stand and pray two (voluntary) rak'ahs before the Maghrib prayer.
Abdullah bin Ahmad recorded it in his Zawa'id (additions); its chain contains a narrator, Hammad bin Shu'ayb, who is da'if (weak).