Ja'far bin Muhammad reports from his father that al-Hasan and al-Husayn (may Allah be pleased with them both) used to pray behind Marwan. The narrator says: Then he asked: "Did they not pray again when they returned to their homes?" He said: "No, by Allah! They did not add anything to the prayer of the imams."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5303