"I saw the Messenger of Allah prostrating for (Surat) Sad." Ibn Abbas said: "It is not one of the resolute prostrations."
Jami` at-Tirmidhi Book 6, Hadith 34
← Previous Hadith "I recited Surat An-Najm to the Messenger of Allah, and he did not prostrate for it."

Jami` at-Tirmidhi Book 6, Hadith 33 Next Hadith → "I said: 'O Messenger of Allah! Surah Al-Hajj has been esteemed by two prostrations?' He said: 'Yes, and whoever does not prostrate for them, he should not recite them.'"

Jami` at-Tirmidhi Book 6, Hadith 35