Musannaf Ibn Abi Shayba 2:38

Abu Bakr narrated to us, he said: Abdullah ibn Idris narrated to us, from al-Shaybani, from Abd al-Aziz ibn Rufay, who said: The final adhan of Abu Mahdhurah was [as follows], and the Messenger of Allah (may Allah bless him and grant him peace) had assigned to him the adhan of Makkah. His final adhan was: Allah is the Greatest, Allah is the Greatest; there is no god but Allah.