Ibn Sirin (may Allah have mercy on him) narrates from some of his companions that Ubayy bin Ka'b (may Allah be pleased with him) led them in prayer in Ramadan, and he would recite the qunut in the last fifteen days of Ramadan.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4629