Jesus has authority to forgive sins (9:1-8). Is one of the things pointed to as evidence of Christ's divinity. I can forgive someone who has injured me but how do I forgive an injury that someone perpetrated on someone else. Only God can forgive in that way.
Matthew's call (9-13) is an example of how the Gospel of Jesus Christ spreads in the world. Matthew is invited to follow Jesus. He is a tax collector (pretty much hated by everyone because they were considered traitors -- working with the occupying Romans to collect taxes -- and because they were notoriously dishonest). When Matthew is converted to following Jesus, he calls his friends and family together and introduces them to Jesus. The gospel travels from us to our natural affinity lines (friends, family, co workers, neighbors). Here Matthew's community are all tax collectors and "sinners". When those who consider themselves righteous see those who have lived outside the faith coming into relationship with Jesus, they usually don't like it. The feeling is kinda like "I've worked hard and earned my righteousness and these people (it is always "these people") just waltz in and are given what I earned. The problem, of course, is that our so called "earned" righteousness is empty, pointless and an illusion.
New movements of the Holy Spirit require new containers. Wine skins, in the first century, were actually animal skins. Old Wine is no longer fermenting, no longer growing. Old Wine in a dried out wine skin won't do any damage. But new wine is vibrant, alive, fermenting, expanding and the dried skin can not expand to contain it. New Wine needs a supple new wine skin that can expand through the fermentation and expansion. The metaphor is essential. Throughout history the Christian church has experienced times and moments of deep spiritual renewal and growth. One characteristic of these movements of renewal is that new forms (forms for worship, for organization, and other understandings) emerge. New Wine (a fresh wind of the Holy Spirit) needs new forms and structures. These historic movements created the monasteries, new denominations, new music, new forms of church government, etc. What will the next fresh wind of the Holy Spirit create among us?
The end of the chapter (37-38) is vital for the life of any Christian community. When the Spirit is moving and people are responding and coming to faith in Christ there is so much need that needs to be cared for a handful of people cannot hope to accomplish it all. In the Christian movement everyone is called by God to serve, everyone is gifted by the Holy Spirit to be in ministry and everyone has been sent to make a difference. Churches that are vital and growing understand this and engage their communities in mission and ministry. And they pray hard that the Lord of the Harvest would send more and more ministers (workers) into the harvest.