Tafsir Al-Jalalayn: An-Najm, Ayah 1

And from his narration on the authority of Ibn 'Abbas that he said regarding the interpretation of Allah's saying (By the Najm when it setteth): '(By the Najm when it setteth) He says: Allah swears by the Qur'an when Gabriel takes it down to Muhammad in instalments (nujuman): one, two, three or four verses at a time. There was a 20 years interval between the first and last verses. When this verse was revealed, 'Utbah Ibn Abi Lahab heard that the Prophet (pbuh) swore by the revelation of the Qur'an in instalment and so he said: �Tell Muhammad that I disbelieve in the instalments of the Qur'an�. When the Prophet (pbuh) was informed of this, he prayed: �O Allah! Set on him one of Your wild beasts�. Later, Allah set on him a lion near Harran that snatched him from among his friends and took him to a place nearby. It tore him apart from head to foot but did not eat him because of his impurity, just as the Prophet (pbuh) had prayed against him. It is also said here Allah swore by the stars when they set,