Musannaf Ibn Abi Shayba 33:276

Abu Mu’awiyah narrated to us, he said: Al-A’mash narrated to us, from ‘Amr ibn Murrah, from Abu Salih, who used to serve Umm Kulthum, daughter of ‘Ali. He said: I entered upon Umm Kulthum while she was combing her hair, and there was a curtain between her and me. I sat waiting for her until she gave me permission. Then Hasan and Husayn came and entered upon her while she was combing her hair. They said, "Will you not feed Abu Salih something?" She said, "Yes." He said: So they brought out a bowl containing broth with grains. I said, "Do you feed me this while you are the leaders (Amirs)?" Umm Kulthum said, "O Abu Salih, how would it be if you had seen the Commander of the Faithful? Citrons were brought to him, and Hasan or Husayn went to take a citron from it, so he snatched it from his hand, then he ordered it to be distributed."