Sahih Bukhari Volume 1, Book 10, Hadith 832

حَدَّثَنَا أَبُو نُعَيْمٍ، قَالَ حَدَّثَنَا الأَعْمَشُ، عَنْ شَقِيقِ بْنِ سَلَمَةَ، قَالَ قَالَ عَبْدُ اللَّهِ كُنَّا إِذَا صَلَّيْنَا خَلْفَ النَّبِيِّ صلى الله عليه وسلم قُلْنَا السَّلاَمُ عَلَى جِبْرِيلَ وَمِيكَائِيلَ، السَّلاَمُ عَلَى فُلاَنٍ وَفُلاَنٍ‏.‏ فَالْتَفَتَ إِلَيْنَا رَسُولُ اللَّهِ صلى الله عليه وسلم فَقَالَ ‏"‏ إِنَّ اللَّهَ هُوَ السَّلاَمُ، فَإِذَا صَلَّى أَحَدُكُمْ فَلْيَقُلِ التَّحِيَّاتُ لِلَّهِ، وَالصَّلَوَاتُ وَالطَّيِّبَاتُ، السَّلاَمُ عَلَيْكَ أَيُّهَا النَّبِيُّ وَرَحْمَةُ اللَّهِ وَبَرَكَاتُهُ، السَّلاَمُ عَلَيْنَا وَعَلَى عِبَادِ اللَّهِ الصَّالِحِينَ‏.‏ فَإِنَّكُمْ إِذَا قُلْتُمُوهَا أَصَابَتْ كُلَّ عَبْدٍ لِلَّهِ صَالِحٍ فِي السَّمَاءِ وَالأَرْضِ، أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ، وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ ‏"‏‏

Narrated By Shaqiq bin Salma : 'Abdullah said, "Whenever we prayed behind the Prophet we used to recite (in sitting) 'Peace be on Gabriel, Michael, peace be on so and so. Once Allah's Apostle looked back at us and said, 'Allah Himself is As-Salam (Peace), and if anyone of you prays then he should say, At-Tahiyatu lil-lahi wassalawatu wat-taiyibatu. AsSalamu 'alalika aiyuha-n-Nabiyu wa rahmatu-l-lahi wa barakatuhu. As-Salam alaina wa ala ibadil-lah is-salihin. (All the compliments, prayers and good things are due to Allah: peace be on you, O Prophet and Allah's mercy and blessings be on you. Peace be on us an on the true pious slaves of Allah). (If you say that, it will be for all the slaves in the heaven and the earth). Ash-hadu an la-ilaha illa-l-lahu wa ash-hadu anna Muhammadan 'abduhu wa Rasuluhu. (I testify that none has the right to be worshipped but Allah and I also testify that Muhammad is His slave and His Apostle)."