Sunan an-Nasa'i, Volume 1, Book 8, Hadith 720 (DarusSalam) ⓘ

It was narrated that Al-Aswad said: "Alqamah and I entered upon 'Abdullah bin Mas'ud and he said to us: 'Have these people prayed?' We said: 'No.' He said: 'Get up and pray.' So we went to stand behind him, and he put one of us on his right and the other on his left, and he prayed with no Adhan and no Iqamah. When he bowed he interlaced his fingers and placed his hands between his knees, and he said: 'I saw the Messenger of Allah doing that.'"

أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا عِيسَى بْنُ يُونُسَ، قَالَ حَدَّثَنَا الأَعْمَشُ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، قَالَ دَخَلْتُ أَنَا وَعَلْقَمَةُ، عَلَى عَبْدِ اللَّهِ بْنِ مَسْعُودٍ فَقَالَ لَنَا أَصَلَّى هَؤُلاَءِ قُلْنَا لاَ ‏.‏ قَالَ قُومُوا فَصَلُّوا ‏.‏ فَذَهَبْنَا لِنَقُومَ خَلْفَهُ فَجَعَلَ أَحَدَنَا عَنْ يَمِينِهِ وَالآخَرَ عَنْ شِمَالِهِ فَصَلَّى بِغَيْرِ أَذَانٍ وَلاَ إِقَامَةٍ فَجَعَلَ إِذَا رَكَعَ شَبَّكَ بَيْنَ أَصَابِعِهِ وَجَعَلَهَا بَيْنَ رُكْبَتَيْهِ وَقَالَ هَكَذَا رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم فَعَلَ ‏.‏