Someone who reads the Bible will know that it has a lot of commands and pointers from God. Each of these laws should be followed as a personal responsibility. Even salvation is personal and should be a private decision. However, there are also certain things that should be done together.
There are various stories in the Bible wherein a group, nation, tribe, or church needed to work together to accomplish a common goal. To be able to work together efficiently, people should set aside their differences and focus on the common goal.
In Joshua, the people warred together to fight off the Canaanites. In Nehemiah, the Israelites worked together to build a wall. In the Book of Acts, those who believed in Christ witnessed together to bring the gospel to the ends of the earth. Working together makes it easier for everyone and accomplishes the goal faster.