Ibn `Abbas reported: (My father) Al-`Abbas sent me to the Messenger of Allah (ﷺ) and he was in the house of my mother's sister Maimuna and I spent that night along with him. He (the Holy Prophet) got up and prayed at night, and I stood up on his left side. He caught hold of me from behind his back and made me stand on his right side.
Source: sunnah.com
Other translations
Arabic
وَحَدَّثَنِي هَارُونُ بْنُ عَبْدِ اللَّهِ، وَمُحَمَّدُ بْنُ رَافِعٍ، قَالاَ حَدَّثَنَا وَهْبُ بْنُ جَرِيرٍ، أَخْبَرَنِي أَبِي قَالَ، سَمِعْتُ قَيْسَ بْنَ سَعْدٍ، يُحَدِّثُ عَنْ عَطَاءٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ بَعَثَنِي الْعَبَّاسُ إِلَى النَّبِيِّ صلى الله عليه وسلم وَهُوَ فِي بَيْتِ خَالَتِي مَيْمُونَةَ فَبِتُّ مَعَهُ تِلْكَ اللَّيْلَةَ فَقَامَ يُصَلِّي مِنَ اللَّيْلِ فَقُمْتُ عَنْ يَسَارِهِ فَتَنَاوَلَنِي مِنْ خَلْفِ ظَهْرِهِ فَجَعَلَنِي عَلَى يَمِينِهِ .
sunnah.com