Musannaf Ibn Abi Shayba 25:305

Ibn Mahdi narrated to us, from Sufyan, from Nusayr, who said: A man said to al-Rabi’ ibn Khuthaym, "Make a bequest to me of your Mushaf (copy of the Quran)." He said: So he looked at a young son of his and said, "And those of [blood] relationship are more entitled [to inheritance] one than the other in the Book of Allah."