بُلُوغُ الْمَرَامِ
Bulugh al-Maram 221
The Book of Prayer
وَعَنْ زَيْدِ بْنِ أَرْقَمَ - رضى الله عنه - قَالَ : { إِنْ كُنَّا لَنَتَكَلَّمُ فِي اَلصَّلَاةِ عَلَى عَهْدِ اَلنَّبِيِّ - صلى الله عليه وسلم -يُكَلِّمُ أَحَدُنَا صَاحِبَهُ بِحَاجَتِهِ , حَتَّى نَزَلَتْ : (حَافِظُوا عَلَى اَلصَّلَوَاتِ وَالصَّلَاةِ اَلْوُسْطَى وَقُومُوا لِلَّهِ قَانِتِينَ) ]اَلْبَقَرَة : 238] , فَأُمِرْنَا بِالسُّكُوتِ , وَنُهِينَا عَنْ اَلْكَلَامِ } مُتَّفَقٌ عَلَيْهِ , وَاللَّفْظُ لِمُسْلِمٍ [1]
Narrated Zaid bin Arqam (RA): We used to talk while engaged in Salat (prayer) during the lifetime of Allah's Messenger (ﷺ) and one would talk with his companion regarding his needs in prayer till (this verse) was revealed: "Guard strictly the prayers, especially the middle prayer; and stand before Allah with obedience," then we were commanded to observe silence (in prayer) and were forbidden to talk. [Agreed upon. This wording is from Muslim].
Sunnah.com reference: Book 2, Hadith 85