Sunan an-Nasa'i, Hadith 1311 ⓘ
It was narrated from Jabir that: The Messenger of Allah used to say in his prayer, after the tashahhud: "The best of word is the word of Allah (SWT) and the best of guidance is the guidance of Muhammad."
أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا يَحْيَى، عَنْ جَعْفَرِ بْنِ مُحَمَّدٍ، عَنْ أَبِيهِ، عَنْ جَابِرٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَقُولُ فِي صَلاَتِهِ بَعْدَ التَّشَهُّدِ " أَحْسَنُ الْكَلاَمِ كَلاَمُ اللَّهِ وَأَحْسَنُ الْهَدْىِ هَدْىُ مُحَمَّدٍ صلى الله عليه وسلم " .
also referenced under: Book 13, Hadith 133 (In-Book) & Volume 2, Book 13, Hadith 1312 (DarusSalam)