Mishkat al-Masabih
Mishkat al-Masabih 208
Chapter - Section 1
Arabic hadith text
وَعَنْ أَنَسٍ قَالَ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا تَكَلَّمَ بِكَلِمَةٍ أَعَادَهَا ثَلَاثًا حَتَّى تُفْهَمَ عَنْهُ وَإِذَا أَتَى عَلَى قَوْمٍ فَسَلَّمَ عَلَيْهِمْ سَلَّمَ عَلَيْهِمْ ثَلَاثًا ". رَوَاهُ الْبُخَارِيُّ
Translation
Anas said that when the Prophet made a statement he repeated itthree times so that it would be understood, and that when he met a company and gave them a salutation he did it three times. Bukharitransmitted it.