Ubayy bin Kaab led them in prayer during Ramadan, and he would recite the qunut during the second half of Ramadan.
حدثنا أحمد بن محمد بن حنبل حدثنا محمد بن بكر أخبرنا هشام عن محمد
أن أبي بن كعب أمهم يعني في رمضان وكان يقنت في النصف الآخر من رمضان
No references are available.
Its isnad is daif. Bayhaqi (2/498) narrated it from the hadith of Abu Dawud with this chain. Ayni said, "It contains an unknown narrator" (Sharh Sunan Abu Dawud, 2/5, no. 1398), and what is meant by that is "some of his companions."