Abu Sa'id Al-Khudri (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "When you hear the Mu'adhdhin (pronouncing the call to Salat), repeat after him what he says."[Al-Bukhari and Muslim]. (DE)
App reference (DE): Book 9, Hadith 48 (DE)
Arabic/English book reference (DE): Book 9, Hadith 1038 (DE)