Abu Umama bin Sahl reported,

I heard Muawiya bin Abu Sufyan, while he was seated on the pulpit, when the muezzin gave the call to prayer.The muezzin said, "Allah is the greatest, Allah is the greatest."Muawiya said, "Allah is the greatest, Allah is the greatest."The muezzin said, "I bear witness that there is no god but Allah."Muawiya said, "And so do I."The muezzin said, "I bear witness that Muhammad is the Messenger of Allah."Muawiya said, "And so do I."When the call to prayer was finished, Muawiya said, "People, I heard the Messenger of Allah ﷺ in this very place, when the muezzin gave the call, say what you have just heard me say."

Azami 10983

Sahih

عن أبي أمامة بن سهل بن حنيف قال

سمعت معاوية بن أبي سفيان وهو جالس على المنبر أذن المؤذن قال: الله أكبر الله أكبر، قال معاوية: الله أكبر الله أكبر، قال: أشهد أن لا إله إلا الله، فقال معاوية: وأنا، فقال: أشهد أن محمدا رسول الله، فقال معاوية: وأنا، فلما قضى التأذين قال: يا أيها الناس، إني سمعت رسول الله ﷺ على هذا المجلس-حين أذن المؤذن- يقول ما سمعتم مني من مقالتي.

الأعظمي 10983صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Supplications, remembrances, and prayer upon the chosen Prophet ﷺ
Chapter
Supplications of adhan and prayer, and what is related to them
Section
What to say upon hearing the call to prayer
Numbering
Jami al-Kamil 10983 (2nd edition)
Azami 10983