Anas bin Malik (May Allah be pleased with him) reported:
When we were in Al-Madinah, the moment the Mu'adhdhin finished the Adhan of the Maghrib prayer, the people hastened to the pillars of the mosque and performed two Rak'ah prayer behind them. A stranger coming into the mosque would think that the obligatory prayer had already been performed because of the number of people performing them.[Muslim]. (JA)
App reference (JA): Book 9, Hadith 135 (JA)
Arabic/English book reference (JA): Book 9, Hadith 1125 (JA)