Sayyiduna Zaid bin Thabit (may Allah be pleased with him) said: I recited Surah An-Najm with the Messenger of Allah (peace and blessings be upon him), and he did not perform prostration in it.
Hadith Referenceسنن دارمي / من كتاب الصللاة / 1511
This hadith indicates the non-obligatory nature of the prostration of recitation (sajdah al-tilawah) in Surah An-Najm, because in the previous narration it has been mentioned that the Messenger of Allah (sallallahu alayhi wa sallam) performed prostration in this surah and all those present also performed prostration, while in this narration the omission of prostration is evident. If the prostration of recitation had been obligatory, then the Messenger of Allah (sallallahu alayhi wa sallam) would never have left it.