بُلُوغُ الْمَرَامِ
Bulugh al-Maram 265
The Book of Prayer
وَعَنْ أَنَسٍ - رضى الله عنه - قَالَ : قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ عُرِضَتْ عَلَيَّ أُجُورُ أُمَّتِي , حَتَّى اَلْقَذَاةُ يُخْرِجُهَا اَلرَّجُلُ مِنْ اَلْمَسْجِدِ } رَوَاهُ أَبُو دَاوُدَ , وَاَلتِّرْمِذِيُّ وَاسْتَغْرَبَهُ , وَصَحَّحَهُ اِبْنُ خُزَيْمَةَ . [1]
Narrated Anas (RA): Allah's Messenger (ﷺ) said: "The rewards of my Ummah (followers) were shown to me, even a peck of dust a man takes out of the mosque." [Reported by Abu Dawud and at-Tirmidhi. The latter graded it Gharib (having a single narrator), and Ibn Khuzaimah graded it Sahih (authentic)].
Sunnah.com reference: Book 2, Hadith 137