(5) باب السُّجُودِ فِي { ص }
Narrated Ibn 'Abbas:
A prostration when reciting Sad is not one of those which are divinely commanded, but I have seen Messenger of Allah (ﷺ) prostrate himself.
Reference: Sunan Abi Dawud 1409
In-book reference: Book 7, Hadith 9
English translation: Book 7, Hadith 1404