Jesus teaches us to rely on Him, to cast our every care on Him, because He cares for us. The miraculous feeding of the 4,000 was the second time the disciples saw Jesus feed a crowd. As the end of Mark 8 shows, Jesus is questioning the disciples about their lack of faith. They saw Him feed 9,000 men, plus women and children with only a few loaves of bread and a few small fish. But the disciples still did not believe, they did not think that God had all things in His control and that He would cause everything to work out for their good.
Why does the Pastor preach? Scripture explains that the role of preaching the Word of God is how saving faith is created: “How then will they call on Him in whom they have not believed? And how are they to believe in Him of whom they have never heard? And how are they to hear without someone preaching? And how are they to preach unless they are sent? As it is written, ‘How beautiful are the feet of those who preach the good news!’ … So faith comes from hearing, and hearing through the Word of Christ” (Romans 10:14-17). The Augsburg Confession, seeing this connection between the Preaching Office and saving faith, summarizes Scripture on the Office of the Holy Ministry in this way: “To obtain [saving, justifying] faith, God instituted the Office of Preaching, giving the Gospel and the Sacraments. Through these, as through means, He gives the Holy Spirit who produces faith, where and when He wills, in those who hear the Gospel. It teaches that we have a gracious God, not through our merit but through Christ’s merit, when we so believe” (AC V 1-3). The whole reason the Pastor preaches is so saving faith can be created, so we know that “we have a gracious God” who loves us and has saved us from our sin by the death and resurrection of Jesus Christ.