مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 1002
Prayer
What may not be done during Prayer and what is permitted - Section 2
وَعَن أم سَلمَة قَالَتْ: رَأَى النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ غُلَامًا لَنَا يُقَالُ لَهُ: أَفْلَحُ إِذَا سَجَدَ نَفَخَ فَقَالَ: «يَا أَفْلَحُ تَرِّبْ وَجْهَكَ» . رَوَاهُ التِّرْمِذِيّ
Umm Salama said: The Prophet (ﷺ) saw a servant of ours called Aflah blowing when he prostrated himself, and said, “Throw dust on your face, Aflah.” Tirmidhi transmitted it.
Mishkat al-Masabih, 1002ضَعِيف (الألباني)