It was narrated that Sa'eed bin Jubair said concerning Ibn 'Umar: "We were with him (Ibn 'Umar) in Jam' (Muzdalifah), and he called the Adhan, then the Iqamah, then he led us in praying Maghrib. Then he said: 'The prayer,' and he led us in praying 'Isha', two Rak'ahs. I said: 'What is this prayer?' He said: 'This is how I prayed with the Messenger of Allah (S.A.W) in this place.'"
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ أَنْبَأَنَا شَرِيكٌ، عَنْ سَلَمَةَ بْنِ كُهَيْلٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عُمَرَ، قَالَ كُنَّا مَعَهُ بِجَمْعٍ فَأَذَّنَ ثُمَّ أَقَامَ فَصَلَّى بِنَا الْمَغْرِبَ ثُمَّ قَالَ الصَّلاَةَ . فَصَلَّى بِنَا الْعِشَاءَ رَكْعَتَيْنِ فَقُلْتُ مَا هَذِهِ الصَّلاَةُ قَالَ هَكَذَا صَلَّيْتُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فِي هَذَا الْمَكَانِ .
sunnah.com