Musannaf Ibn Abi Shayba 3:5191

Waki’ narrated to us, [who] said: Bastam narrated to us, [who] said: I asked Abu Ja’far about praying with the commanders (umara’). He said: "Pray with them, for we pray with them. Al-Hasan and Al-Husayn used to hasten to the prayer behind Marwan." I said: "The people claim that this is out of taqiyya (precautionary dissimulation)." He said: "And how [could that be], when Al-Hasan ibn Ali used to insult Marwan to his face while he was on the pulpit, until he (Marwan) turned away?"