The Letter to the Hebrews sees Jesus as fulfilling the promise in Jeremiah 32. God was going to establish a new covenant and write it on the hearts and minds of believers so that everyone can know God - not know about God but know God, directly and personally. The need for instructing one another about God would pass away. When we have a personal relationship and friendship with Jesus Christ, we know and experience God. Jesus chose twelve men - and why He chose these twelve, only the Lord knows. They were a collection of human weaknesses and failures, and they would let Him down. But that is part of the revelation - how God can do fantastic things with ordinary people. He gave them the power and authority they needed to heal and cast out demons. Their job was to proclaim the good news. And that is our job too. We are as weak and fallible as the Apostles, but the Lord can work wonders if we have faith and open hearts.