Abdullah ibn abi Sarh, the foster brother of Uthman Affan, was a writer of the Quran. According to some sources, he left Islam because he was able to influence the revelation with his own words and he doubted Muhammad was receiving revelation from God. The first source which is the seerah of Ibn Hisham says that he was a companion who apostated and Prophet Muhammad wanted him executed. However Uthman interceded for him and requested immunity, which was granted. However according to our sources, Prophet Muhammad still wished that he would have been killed and questioned his companion as to why he didnt kill him. This was also mentioned in Tabaqat al Kabir by Ibn Saad
It was narrated from Mus’ab bin Sa’d that his father said:“On the day of the Conquest of Makkah, the Messenger of Allah [SAW] granted amnesty to the people, except four men and two women. He said: ‘Kill them, even if you find them clinging to the covers of Ka’bah.’ (They were) ‘Ikrimah bin Abi Jahl, ‘Abdullah bin Khatal, Miqyas bin Subabah and ‘Abdullah bin Sa’d bin Abi As-Sarh. ‘Abdullah bin Khatl was caught while he was clinging to the covers of Ka’bah. Sa’eed bin Huraith and ‘Ammar bin Yasir both rushed toward him, but Sa’eed, who was the younger of the two, got there before ‘Ammar, and he killed him. Miqyas bin Subabah was caught by the people in the marketplace, and they killed him. ‘Ikrimah traveled by sea, and he was caught in a storm. The crew of the ship said: ‘Turn sincerely toward Allah, for your (false) gods cannot help you at all in this situation.’ ‘Ikrimah said: ‘By Allah, if nothing came to save me at sea except sincerity toward Allah then nothing else will save me on land. O Allah, I promise You that if You save me from this predicament I will go to Muhammad [SAW] and put my hand in his, and I am sure that I will find him generous and forgiving.’ So he came, and accepted Islam. ‘Abdullah (bin Sa’d) bin Abi Sarh hid in the house of ‘Uthman bin ‘Affan, and when the Messenger of Allah [SAW] called the people to give their Oath of Allegiance, he brought him, and made him stand before the Prophet [SAW]. He (‘Uthman) said: ‘O Messenger of Allah! Accept the allegiance of ‘Abdullah.’ He raised his head and looked at him three times, refusing his allegiance each time, then he accepted his allegiance after three times.
Then he turned to his Companions and said: ‘Was there not any sensible man among you who would get up when he saw me refusing to give him my hand and kill him?’
They said: ‘We did not know, O Messenger of Allah, what was in your heart. Why did you not gesture to us with your eyes?’ He said: ‘It is not befitting for a Prophet that his eyes be deceitful.'” (Nasai)
The details as to Abi Sarh saying that he was able to change the words used in the Quran are mentioned in Al-Sira by al-‘Iraqi. The story of Abi Sarh being able to predict the next phrase of the Quran in Al-Baidawi. I don’t know how authentic these stories are. However this is very similar to the just in time revelations issue and I would not be surprised if it was true. At the very least we know that Muhammad wanted him killed because he used to receive revelation and he was a major threat to Islam.
With all due respect, why does the one coming with truth, the perfection of creation need to murder people to spread his message? Does God truly need to murder people in order to protect the authenticity of his message?
Read more here: Answering Islam – Abdullah ibn Abi Sarh
Also read Abrogations in the Quran.