Concept:Abdullah ibn Saʿd ibn Abī Sarḥ, one of the Prophet's scribes, was expelled from Madinah because he sided with the Quraysh after abandoning Islam.
Explanation:Abdullah ibn Saʿd ibn Abī Sarḥ was among those who wrote down the Qur'anic revelations for the Prophet.
He began to make alterations and suggestions in the wording of the revelation.
This led him to doubt that the revelation was truly from God, so he left Islam.
After leaving Islam, he joined the Quraysh and associated with them.
For this association with the Quraysh, he was expelled from Madinah.
His earlier tampering with the Qur'an was the reason he lost faith, but the act that caused his expulsion was his alignment with the Quraysh.
Later, after the conquest of Makkah, the Prophet ordered his punishment, but he was eventually pardoned.
Answer:A. Associating with the Quraysh.