When Mecca fell to Muhammad's plunderous and conquering Jihadi brigands in 630, he did not want to kill everyone for many reasons. These lucky ones included those, who had hid in the holy ka'ba, because Muhammad had promised to Abu Sufian to spare. But he didn't keep his word. Muhammad condemned to death an unlucky few, 10–12 men and women, even if they had hid in the holiest spot inside the Ka'ba. One of those, chosen for Muhammad's vengeance, was Abdullah ibn Sa'd ibn Abi Sarh (Abdullah, son of Sa'd, son of Abi Sarh). This Abdullah was one of Muhammad's Qur'anic scribes in Medina.

The late an Iranian scholar on Islam Ali Dashti, murdered at an old age by the current Iranian regime of brutal Mullahs, was an honest researcher. Although recent, I trust his research on Islam as much as the early Sirats. In his book "Twenty Three Years", Dashti writes the following regarding Abdullah:

[Abdullah] had been one of the scribes employed at Medina to write down the 'revelations'. On a number of occasions, with Muhammad's consent, he changed the closing words of verses. For example, when Muhammad said "And God is mighty and wise", Abdullah Sarh suggested 'knowing and wise', and the prophet answered that there was no objection. Having observed a succession of changes of this type, Abdullah renounced Islam on the ground that the revelations, if from God, could not be changed at the prompting of a scribe such as himself. After his apostasy, he went to Mecca and joined the Qorayshites. (Page 98)

This is an interesting quote. An inquisitive mind, be it a Muslim or not, is justified to wonder how much of the Qur'an was Muhammad's and how much of it was "improvements" suggested by his scribes. We know about Abdullah the scribe for his famous death sentence. But how many scribes were there? How many of them suggested "improvements" or "changes" to Muhammad to make the Qur'anic verses look more "polished", more "beautiful". Obviously, we will never know. They are long gone; most of them must have kept silence fearing Abdullah's fate.

You see, Abdullah became an apostate because he saw what Muhammad was doing first hand. He was not receiving anything from the heaven. He was a mere thug; his desire in life was to control people by whatever means necessary; his alleged divine revelations, all invented by himself, was one such instrument, indeed the most lethal one. The above story is a clear evidence of this claim.

Muslims may wish to reject the works of Dashti: a man who, lived in our life-time and died just a few decades ago (early 1980s). Even if one wishes to disregard Dashti's work, despite high regards about  the trustworthiness and honesty, which he exercised is his research, this claim is supported by other original sources too. Let's see what Ibn Ishaq has to say on the issue in his "Sirat Rasul Allah" (A. Guillaume's translation) (I added some words in parenthesis to better clarify things to the reader):

The apostle had instructed his commanders when they entered Mecca only to fight those who resisted them, except a small number who were to be killed even if they were found beneath the curtains of the Kaba. Among them was Abdullah Sa'd, brother of the B. Amir Luayy. The reason he ordered him to be killed was that he had been a Muslim and used to write down revelation; then he apostatized and returned to Quraysh (i.e., to Mecca) and (after Mecca taken) fled to Uthman Affan (prophet's son-in-law) whose foster brother he was. The latter hid him until he brought him to the apostle after the situation in Mecca was tranquil, and asked that he might be granted immunity. They allege that the apostle remained silent for a long time till finally he said "yes". When Uthman had left he (Muhammad) said to his companions who were sitting around him, ‘I kept silent so that one of you might get up and strike off his head!' One of the Ansar said, ‘Then why didn't you give me a sign, O apostle of God?' He answered that a prophet does not kill by pointing (Page 550).

What saved Abdullah's life is Uthman. Uthman was his foster brother, also very close to the prophet—a son-in-law; his words carried some weight to Muhammad. Even then, Muhammad really wanted him dead. He could not forgive him for leaving Medina and becoming an apostate. Abdullah also new too much about the "revelations" that Muhammad claimed he had received from heaven.

I guess, and this is my "Ijtihad" for the day, that when Gabriel gave Muhammad the "revelations", something got lost in the translation; so, he needed the help of the scribes to get back the "original" language of the revelations as "truly" revealed by Gabriel. True Muslims should be happy then that there were Qur'anic scribes, who helped keep Muhammad's revelation in the original form, saved anything that could have been lost in the translation!

obviously, Abdullah and people like him were a threat to Muhammad's credibility as a prophet,  and to that of the Qur'an. He was better off having rebels like him silenced once and for all. That is why the prophet of mercy wanted Abdullah dead. However, Abdullah's circumstances, lobbying power of his near ones, particularly his foster brother Uthman, saved his neck. He survived the day; others, even with lesser offense, were not so lucky.