مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3904
Musnad of Abdullah bin Mas'ood
It was narrated that Khumair bin Malik said: Instructions were issued to replace the Mushafs, and Ibn Masood (رضي الله عنه) said: Whoever among you is able to keep his Mushaf, let him do so, for the one who keeps something will come with it on the Day of Resurrection. Then he said: I learned seventy soorahs from the lips of the Messenger of Allah (ﷺ); should I abandon what I learned from the Messenger of Allah (ﷺ)?
Musnad Ahmad 3929A saheeh hadeeth, al-Bukhari (5000) and Muslim (2462) its is