Ibn Abbas said, "Surah Sad is not among the obligatory prostrations, yet I saw the Prophet ﷺ prostrate during it."
{ص} ليس من عزائم السجود، وقد رأيت النبي ﷺ يسجد فيها.
Bukhari narrated it in the chapter on the prostration of the Quran (1069) from Sulayman bin Harb and Abu Numan, who both said, "Hammad narrated to us, from Ayub, from Ikrima, from Ibn Abbas," and he mentioned it.