Not graded
Riyad as-Salihin 1125
وعنه قال: كنا بالمدينة فإذا أذن المؤذن لصلاة المغرب ابتدروا السواري، فركعوا ركعتين، حتى إن الرجل الغريب ليدخل المسجد فيحسب أن الصلاة قد صليت من كثرة من يصليهما. ((رواه مسلم)).
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].
Reported by Muslim (No. 837). Cited in Riyad as-Salihin (No. 1125).