Musannaf Ibn Abi Shayba 21:110

Waki’ narrated to us, from Sufyan, from Salamah ibn Kuhayl, from Abu al-Darda’ al-Ansari, who said: ‘A’ishah said to her sister’s son: “Indeed, for you to supplicate for yourself is better than for the storyteller (al-qass) to supplicate for you.”