وَعَنْ اِبْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا
قَالَ: «صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: لَيْسَتْ مِنْ عَزَائِمِ اَلسُّجُودِ، وَقَدْ رَأَيْتُ رَسُولَ اَللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ (يَسْجُدُ فِيهَا» رَوَاهُ اَلْبُخَارِيُّ. 11) صحيح
A prostration while reciting Surat Sad (Surah 38) is not one of the ‘Azaaim (those which are always required), but I have seen the Messenger of Allah (sallallahu alayhi wa sallam) prostrating while reciting it.’
Bulugh al-Maram 417, Book 2, The Book of Prayer, Hadith 238. 1 min read