وعن عبد الله بن مغفل، رضي الله عنه عن النبي صلى الله عليه وسلم قال‏:‏ ‏"‏صلوا قبل المغرب‏"‏ قال في الثالثة‏:‏ ‏"‏لمن شاء‏"‏ ‏(‏‏(‏رواه البخاري‏)‏‏)‏‏.‏

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].