Musannaf Ibn Abi Shayba 26:8

Waki’ narrated to us, he said: Musa ibn ‘Ali ibn Rabah narrated to us, from his father, that ‘Umar addressed the people at al-Jabiyah. He praised Allah and extolled Him, then said: "Whoever wishes to ask about the Qur’an, let him come to Ubayy ibn Ka’b. And whoever wishes to ask about the laws of inheritance (fara’id), let him come to Zayd ibn Thabit."