Sunan an-Nasa'i, hadith 660

أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، عَنْ وَكِيعٍ، قَالَ حَدَّثَنَا ابْنُ أَبِي ذِئْبٍ، عَنِ الزُّهْرِيِّ، عَنْ سَالِمٍ، عَنْ أَبِيهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم جَمَعَ بَيْنَهُمَا بِالْمُزْدَلِفَةِ صَلَّى كُلَّ وَاحِدَةٍ مِنْهُمَا بِإِقَامَةٍ وَلَمْ يَتَطَوَّعْ قَبْلَ وَاحِدَةٍ مِنْهُمَا وَلاَ بَعْدُ ‏.‏

It was narrated from Salim, from his father, that the Prophet (S.A.W) joined them (Maghrib and 'Isha') in Al-Muzdalifah, and he prayed each of them with an Iqamah, and he did not offer any voluntary prayer before or after either of them