It was narrated from Abu Sa'eed Al-Khudri that the Messenger of Allah (ﷺ) said:
"When you hear the call, say what the Mu'adhdhin says." (JA)
English reference (JA): Vol. 1, Book 7, Hadith 674 (JA)
Arabic reference (JA): Book 7, Hadith 681 (JA)