Sunan an-Nasa'i 1174

أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ بْنُ سَعْدٍ، عَنْ أَبِي الزُّبَيْرِ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، وَطَاوُسٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُعَلِّمُنَا التَّشَهُّدَ كَمَا يُعَلِّمُنَا الْقُرْآنَ وَكَانَ يَقُولُ ‏ "‏ التَّحِيَّاتُ الْمُبَارَكَاتُ الصَّلَوَاتُ الطَّيِّبَاتُ لِلَّهِ سَلاَمٌ عَلَيْكَ أَيُّهَا النَّبِيُّ وَرَحْمَةُ اللَّهِ وَبَرَكَاتُهُ سَلاَمٌ عَلَيْنَا وَعَلَى عِبَادِ اللَّهِ الصَّالِحِينَ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ ‏"‏ ‏.‏

It was narrated that Ibn 'Abbas said:"The Messenger of Allah (ﷺ) used to teach us the tashahhud as he taught us the Quran, and he used to say: : 'At-tahiyyatu lillahi was-salawatu wat-tayyibat, as-salamu 'alaika ayyuhan-Nabiyyu wa rahmatAllahi wa barakatuhu. As-salamu 'alaina wa 'ala 'ibad illahis-salihin, ash-hadu an la ilaha ill-Allah wa ash-hadu anna Muhammadan 'abduhu wa rasuluhu (All compliments, prayers and pure words are due to Allah. Peace be upon you, O Prophet, and the mercy of Allah (SWT) and his blessings. Peace be upon us and upon the righteous slaves of Allah (SWT). I bear witness that none has the right to be worshipped except Allah and I bear witness that Muhammad is His slave and Messenger

Reference

Sunan an-Nasa'i 1174

In-book

Book 12, Hadith 146