Musannaf Ibn Abi Shayba 3:2457

Waki' narrated to us, from Sufyan, from Jabir, from 'Amir and others, regarding a man who intended to say "Sami' Allahu liman hamidah" (Allah hears those who praise Him), but instead said "Allahu Akbar" (Allah is the Greatest). They said: There is no forgetfulness (sujud al-sahw) upon him.