(Hast thou not seen those unto whom a portion of the Scripture hath been given, how they believe in idols and false deities…) [4:51]. Muhammad ibn Ibrahim ibn Muhammad ibn Yahya informed us> his father> Muhammad ibn Ishaq al-Thaqafi> 'Abd al-Jabbar ibn al-'Ala'> Sufyan> 'Amr>> 'Ikrimah who said: “When Huyayy ibn Akhtab and Ka'b al-Ashraf went to the people of Mecca they were asked: 'You are people of Scripture and ancient knowledge, so tell us about us and Muhammad?' 'What do you have to do with Muhammad?' he said. They said: 'We slaughter high-humped camels, give milk on top of water for others to drink, we assist those who are wronged, we do not severe ties of kinship and give water to the pilgrims and our religion is ancient while Muhammad's religion is new'. The Jews said: 'Rather, you are better than him and more guided in your way'. And so Allah, exalted is He, revealed (Hast thou not seen those unto whom a portion of the Scripture hath been given, how they believe in idols and false deities) up to His words, exalted is He, (… and he whom Allah hath cursed, thou (O Muhammad) wilt find for him no helper) [4:52]”. The commentators of the Qur'an said: “After the Battle of Uhud, Ka'b ibn al-Ashraf went to Mecca, accompanied by seventy riders, in order to ally themselves with Quraysh against the Messenger of Allah, Allah bless him and give him peace, and break the covenant which they had with Allah's Messenger, Allah bless him and give him peace. Ka'b was the guest of Abu Sufyan while the other Jews were accommodated in the houses of Quraysh. The people of Mecca said: 'Your are people of Scripture and Muhammad has a Scripture and we are not completely sure that this is a scheme that you devised. So if you want us to go along with you, you have to prostrate to these two idols and believe in them', hence Allah's saying (they believe in idols and false deities). Ka'b then said to the people of Mecca: 'Let there be thirty of us and thirty of you; we shall all go to the Ka'bah and cling to it and promise the Lord of the House that we will do our best to fight Muhammad'.
Asbab Al-Nuzul by Al-Wahidi , trans. Mokrane Guezzou