Abu Shu'bah narrates: I saw Sayyiduna Imam Hasan (may Allah be pleased with him) and Sayyiduna Imam Husayn (may Allah be pleased with him) performing tawaf after Asr and praying two rak'ahs.
Imam al-Tabarani recorded it in al-Mu'jam al-Kabir. This narrator Abu Shu'bah is al-Bakri, as al-Mizzi mentioned; I have not found anyone giving his biography.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الحج / 5509