Musnad Ahmad 936:2

Abdullah narrated to us, Muhammad ibn Abi Bakr al-Muqaddami narrated to me, Abd al-Wahhab al-Thaqafi narrated to us, and Abdullah narrated, and Wahb ibn Baqiyyah narrated to me, Khalid al-Wasiti informed us. Al-Thaqafi said in his hadith: Abu Mas'ud al-Jurayri narrated to us. And Wahb said: Khalid informed us, from al-Jurayri, from Abu Nadrah, who said: Ubayy ibn Ka'b said: "Prayer in a single garment is a Sunnah; we used to do it with the Messenger of Allah, may Allah bless him and grant him peace, and it was not considered a fault in us." Ibn Mas'ud said: "That was only when there was a scarcity of garments. But when Allah has granted abundance, then prayer in two garments is purer." *** Abd al-Rahman ibn Mahdi, Hasan ibn Musa, and Affan narrated to us, they said: Hammad ibn Salamah narrated to us, from Thabit—and Affan said: Thabit informed us—from Abu Rafi', from Ubayy ibn Ka'b, that the Messenger of Allah, may Allah bless him and grant him peace, and Abdullah narrated to us, Hudbah ibn Khalid narrated to us, Hammad narrated to us, from Thabit, from Abu Rafi', from Ubayy ibn Ka'b: That the Messenger of Allah, may Allah bless him and grant him peace, "used to perform I'tikaf in the last ten days of Ramadan. He traveled one year, so he did not perform I'tikaf. When the following year came, he performed I'tikaf for twenty days." *** Abd al-Razzaq narrated to us, Sufyan informed us, from Sa'id al-Jurayri, from Abu al-Sulayl, from Abdullah ibn Rabah, from Ubayy. And Abdullah narrated to us, Ubayd Allah al-Qawariri narrated to me, Ja'far ibn Sulayman narrated to us, al-Jurayri narrated to us, from some of his companions, from Abdullah ibn Rabah, from Ubayy: That the Prophet, may Allah bless him and grant him peace, asked him: "Which verse in the Book of Allah is the greatest?" He said: "Allah and His Messenger know best." He repeated it several times. Then Ubayy said: "Ayat al-Kursi." He said: "May knowledge be pleasant to you, Abu al-Mundhir. By the One in Whose hand is my soul, it has a tongue and two lips that sanctify the King at the foot of the Throne." This is the wording of the hadith of Ubayy from Abd al-Razzaq.