Imagine finding the remains of a 1925 Model T Ford pickup and deciding to completely restore it, i.e. to return it to its original condition. You would have to know exactly what it was like when it was new and faithfully follow that pattern without addition or subtraction.
Over 200 years ago some people realized that the church of the 19th century was very different from the church of the first century. Instead of unity, there was widespread division. Acts 9:31; 1 Corinthians 4:17. They started what is now known as the Restoration Movement in an attempt to return the church to its original condition because the changes were prohibited, predicted, and counterproductive. Jude 3; Galatians 1:8-9; 2 Timothy 4:1-5; John 17:20-23.
For further reading, click on the sermon lesson sheet