Musannaf Ibn Abi Shayba 26:9

Waki' narrated to us, he said: Al-Mas'udi narrated to us, from Al-Qasim ibn 'Abd al-Rahman, he said: 'Abdullah said: "Learn the Qur'an and the laws of inheritance (al-fara'id), for it is imminent that a man will be in need of knowledge he used to know, or he will remain among a people who do not know."