Musannaf Ibn Abi Shayba 1:2101

Waki’ narrated to us, he said: Sufyan narrated to us, from Layth, from Mujahid, and from Jabir, from al-Sha’bi, that they both disliked that a person in a state of major ritual impurity (junub) should write "In the name of Allah, the Most Gracious, the Most Merciful."