It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him), he says: No companion had more knowledge of the hadiths of the Messenger than me except Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with him), and the reason for this was that he used to write down the hadiths and memorize them, while I only memorized them orally and did not write them. He sought permission from the Messenger of Allah (peace and blessings be upon him) to write down the hadiths, so he granted him permission.