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It was narrated that 'Amr bin Dinar said: "I heard Jabir bin 'Abdullah say: 'The Messenger of Allah (ﷺ) said: "If any one of you comes and the Imam has appeared, let him pray two Rak'ahs. Shu'bah (one of the narrators) said: "On Friday."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا خَالِدٌ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ عَمْرِو بْنِ دِينَارٍ، قَالَ سَمِعْتُ جَابِرَ بْنَ عَبْدِ اللَّهِ، يَقُولُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " إِذَا جَاءَ أَحَدُكُمْ وَقَدْ خَرَجَ الإِمَامُ فَلْيُصَلِّ رَكْعَتَيْنِ " . قَالَ شُعْبَةُ يَوْمَ الْجُمُعَةِ .
sunnah.com