When God said He wanted to do a “new thing” He meant it literally concerning the time shortly to come. And, the word new, meant that it would be completely new, nothing at all like the previous thing. In this He referred to the day of Pentecost, the birth of the Church, and the reforming of His people with relationships through Him as the common ground between them.
The Children of Israel left Egypt for a “new” way of life, and yet the Egyptian way of living was all they knew, and they continued to be enslaved by it because of their old ways of thinking. We have all heard sermons where the preacher said that “it was easier to get them out of Egypt, than to get Egypt out of them.” This is a problem common to all of us.
So God has this New Wineskin, and it's very different to what we have known. The whole wineskin is built with relationships. In 1 Peter 2:4-5 it says “As you come to him, the living Stone—rejected by humans but chosen by God and precious to him—you also, like living stones, are being built into a spiritual house to be a holy priesthood, offering spiritual sacrifices acceptable to God through Jesus Christ.” (NIV) And so this and many other Scriptures show us that God is trying to build something together by joining people together. This means the sharing of our lives together and the giving of hearts and being one that way.
Previous to the Day of Pentecost, the apostles and the disciples were a group of people, and were one because of the fact that they had something in common, and that was Christ. However they didn't get agree with each other. They fought about who was the greatest, and there was rivalry between them. We refer to this as the spirit of competition. Their hearts were not synchronised by the Holy Spirit and were not in step with God or each other.
However after Pentecost they had one heart and one mind, and worked together for the sake of the Kingdom. There had been a change in the way they saw each other, and felt about each other. Their lives had been knit together.
It was THAT kind of joining that IS the new wineskin, the Church. It is that kind of togetherness which builds the church and makes it a holy place. It is that kind of people that is the new wineskin. Into a people like that, the Holy Spirit (the wine) can be poured out, and can be contained for the purposes of God.
As you can no doubt see, the new wineskin is hard to define, especially if you are still so accustomed to the old way of doing things, or the way you suppose Christianity should be. It's hard to see, and yet once you see it (like those 3D image books) you will never be able to unsee it, and things will be permanently different for you.
If we could describe the new wineskin in one word, we would say relationships. However if we could describe it with more detail we would say the new wineskin is “father-son relationships in the Body of Christ.” It is the way people love their leaders and the way that leaders love their people, and the way they work together, just like God the Father and God the Son did. They are our example. If this doesn't make immediate sense, then continue reading because as the next section will reveal, this is the nature of God Himself.