http://www.witness-pioneer.org/vil/Articles/companion/zayd_ibn_thabit.htm
Zayd's enthusiasm and skill were obvious. When the Prophet felt confident of his faithfulness in the discharge of duties and the care, precision and understanding with which he carried out tasks,
he entrusted Zayd with the weighty responsibility of recording the Divine revelation.
When any part of the Quran was revealed to the Prophet,
he often sent for Zayd and instructed him to bring the writing materials, "the parchment, the ink-pot and the scapula", and write the revelation.
Zayd was not the only one who acted as a scribe for the Prophet. One source has listed forty-eight persons who used to write for him. Zayd was very prominent among them. He did not only write but during the Prophet's time he collected portions of the Quran that were written down by others and arranged these under the supervision of the Prophet. He is reported to have said:
"
We used to compile the Quran from small manuscripts in the presence of the Prophet." In this way, Zayd experienced the Quran directly from the Prophet himself. It could be said that he grew up with the verses of the Quran, understanding well the circumstances surrounding each revelation. He thus became well-versed in the secrets of the Shariah and at an early age gained the well-deserved reputation as a leading scholar among the companions of the Prophet.