Hadith 1199 - Actions while Praying - Sahih Al-Bukhari - صحيح البخاري - Collection of Actions, Sayings and Teachings of Prophet Muhammad (صلى الله عليه و سلم) - Kutub as-Sittah

21. Actions while Praying - كتاب العمل فى الصلاة

2) Chapter: What speech is prohibited during As-Salat

Narrated `Abdullah:

We used to greet the Prophet (ﷺ) while he was praying and he used to answer our greetings. When we returned from An-Najashi (the ruler of Ethiopia), we greeted him, but he did not answer us (during the prayer) and (after finishing the prayer) he said, "In the prayer one is occupied (with a more serious matter)."

Reference: 1199
English reference: Vol. 2, Book 22, Hadith 290
In-book reference: Book 21, Hadith 2
Grade: Sahih
Read this hadith from Darussalam Collection

2) باب مَا يُنْهَى عَنْهُ مِنَ الْكَلاَمِ فِي الصَّلاَةِ

حَدَّثَنَا ابْنُ نُمَيْرٍ، حَدَّثَنَا ابْنُ فُضَيْلٍ، حَدَّثَنَا الأَعْمَشُ، عَنْ إِبْرَاهِيمَ، عَنْ عَلْقَمَةَ، عَنْ عَبْدِ اللَّهِ ـ رضى الله عنه ـ قَالَ كُنَّا نُسَلِّمُ عَلَى النَّبِيِّ صلى الله عليه وسلم وَهُوَ فِي الصَّلاَةِ فَيَرُدُّ عَلَيْنَا، فَلَمَّا رَجَعْنَا مِنْ عِنْدِ النَّجَاشِيِّ سَلَّمْنَا عَلَيْهِ فَلَمْ يَرُدَّ عَلَيْنَا وَقَالَ ‏‏‏.‏ "‏ إِنَّ فِي الصَّلاَةِ شُغْلاً ‏"