Musannaf Ibn Abi Shayba 1:1795

Mu'awiyah ibn Hisham narrated to us, he said: Sulayman ibn Qarm narrated to us, from Abu Habib, from a man from the people of the Hijaz, from Abdullah ibn al-Zubayr, from the Prophet (may Allah bless him and grant him peace), who said: "Were it not that I would make it difficult for my nation, I would have commanded them to use the siwak at every prayer."