Sahih Bukhari Volume 2, Book 21, Hadith 1203

حَدَّثَنَا عَمْرُو بْنُ عِيسَى، حَدَّثَنَا أَبُو عَبْدِ الصَّمَدِ عَبْدُ الْعَزِيزِ بْنُ عَبْدِ الصَّمَدِ، حَدَّثَنَا حُصَيْنُ بْنُ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي وَائِلٍ، عَنْ عَبْدِ اللَّهِ بْنِ مَسْعُودٍ ـ رضى الله عنه ـ قَالَ كُنَّا نَقُولُ التَّحِيَّةُ فِي الصَّلاَةِ وَنُسَمِّي، وَيُسَلِّمُ بَعْضُنَا عَلَى بَعْضٍ، فَسَمِعَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم فَقَالَ ‏"‏ قُولُوا التَّحِيَّاتُ لِلَّهِ وَالصَّلَوَاتُ وَالطَّيِّبَاتُ، السَّلاَمُ عَلَيْكَ أَيُّهَا النَّبِيُّ وَرَحْمَةُ اللَّهِ وَبَرَكَاتُهُ، السَّلاَمُ عَلَيْنَا وَعَلَى عِبَادِ اللَّهِ الصَّالِحِينَ، أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ، فَإِنَّكُمْ إِذَا فَعَلْتُمْ ذَلِكَ فَقَدْ سَلَّمْتُمْ عَلَى كُلِّ عَبْدٍ لِلَّهِ صَالِحٍ فِي السَّمَاءِ وَالأَرْضِ ‏"‏‏

Narrated By 'Abdullah bin Masud : We used to say the greeting, name and greet each other in the prayer. Allah's Apostle heard it and said: "Say, 'At-tahiyyatu lil-lahi was-salawatu wat-taiyibatu. Assalamu 'Alaika aiyuha-n-Nabiyu wa-rahmatu-l-lahi wa-barakatuhu. Assalamu alaina wa-'ala 'ibadi-l-lahi as-salihin... Ashhadu an la ilaha illa-l-lah wa ashhadu anna Muhammadan 'abdu hu wa Rasuluh. (All the compliments are for Allah and all the prayers and all the good things (are for Allah). Peace be on you, O Prophet, and Allah's mercy and blessings (are on you). And peace be on us and on the good (pious) worshipers of Allah. I testify that none has the right to be worshipped but Allah and that Muhammad is His slave and Apostle.) So, when you have said this, then you have surely sent the greetings to every good (pious) worship per of Allah, whether he be in the Heaven or on the Earth."