What may not be done during Prayer and what is permitted - Section 2 Mishkat al-Masabih 1002
Arabic hadith text
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
Translation
Umm Salama said
The Prophet saw a servant of ours called Aflah blowing when he prostrated himself, and said, “Throw dust on your face, Aflah.” Tirmidhi transmitted it.