سُنَنُ النَّسَائِيِّ
Sunan an-Nasa’i 7
The Book of Purification
Permitting The Usage Of Siwak In The Afternoon For One Who Is Fasting
أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، عَنْ مَالِكٍ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ لَوْلاَ أَنْ أَشُقَّ عَلَى أُمَّتِي لأَمَرْتُهُمْ بِالسِّوَاكِ عِنْدَ كُلِّ صَلاَةٍ .
It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said: "Were it not that it would be too difficult for my Ummah, I would have commanded them to use the Siwak at (the time of) every Salah."
Sunan an-Nasa'i, 7Sahih (Darussalam)