The Bible
Doctrine and Covenants 21
1–3, Joseph Smith is called to be a seer, translator, prophet, apostle, and elder; 4–8, His word will guide the cause of Zion; 9–12, The Saints will believe his words as he speaks by the Comforter.

5For his word ye shall receive, as if from mine own mouth, in all patience and faith.
10Wherefore it behooveth me that he should be ordained by you, Oliver Cowdery mine apostle;