Sunan Abi Dawud Book 42, Hadith 28
Qurrah b. Khalid used to tell us: O young people! Do not think that al-Hasan denied predestination, for his opinion (i.e., belief) was sunnah and sight.
I heard Ayyub say: Two kinds of people have lied to al-Hasan: people who believed in free will and they intended that they publicise their belief by it; and people who had enmity with and hostility (for al-Hasan), saying: Did he not say so and so? Did he not say so and so?
If we learnt that the remark of al-Hasan would reach the extent that it has reached, we would write a book for his withdrawal and call witnesses to him; but we said: This is a remark that surprisingly came out (from him) and it will not be transmitted to others.