Musannaf Ibn Abi Shayba 3:1195

Waki’ narrated to us, from Sufyan, from Zayd al-‘Ammi, from Abu al-‘Aliyah, who said: The Messenger of Allah (may Allah bless him and grant him peace) estimated his recitation in the Dhuhr prayer to be approximately [the length of] *Alif-Lam-Mim Tanzil* (Surah as-Sajdah).