Musannaf Ibn Abi Shayba 23:136

Abu Usama narrated to us, from Jarir ibn Hazim, who said: Isa ibn Asim narrated to me, who said: Adi ibn Adi narrated to me, saying: Umar ibn Abd al-Aziz wrote to me: "To proceed: Indeed, faith has obligations, laws, limits, and practices. Whoever completes them has completed faith, and whoever does not complete them has not completed faith. If I live, I will clarify them to you so that you may act upon them. And if I die before that, I am not eager for your company."