كتاب صلاة الليل
7  
Tahajjud

Yahya related to me from Malik from Sharik ibn Abdullah ibn Abi Namir that Abu Salama ibn Abd ar-Rahman said, "Some people heard the iqama and started to pray. The Messenger of Allah, may Allah bless him and grant him peace, came out and said, 'Are you doing two prayers at the same time? Are you doing two prayers at the same time?' That was about the subh prayer and the two rakas before subh."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ شَرِيكِ بْنِ عَبْدِ اللَّهِ بْنِ أَبِي نَمِرٍ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، أَنَّهُ قَالَ سَمِعَ قَوْمٌ الإِقَامَةَ، فَقَامُوا يُصَلُّونَ فَخَرَجَ عَلَيْهِمْ رَسُولُ اللَّهِ صلى الله عليه وسلم فَقَالَ ‏ "‏ أَصَلاَتَانِ مَعًا أَصَلاَتَانِ مَعًا ‏"‏ ‏.‏ وَذَلِكَ فِي صَلاَةِ الصُّبْحِ فِي الرَّكْعَتَيْنِ اللَّتَيْنِ قَبْلَ الصُّبْحِ ‏.‏
Sunnah.com reference : Book 7, Hadith 31
USC-MSA web (English) reference : Book 7, Hadith 31
Arabic reference : Book 7, Hadith 285