It has been demonstrated many times that the habits of the people we spend time with will become our habits. We will assimilate their speech, actions and even begin to pick up on their belief patterns. We will begin to read and watch what is important to them. Even our music preferences will reflect theirs.
The author of Hebrews is reminding us to stay close to those whose God is our God. He is also reminding us that it is easy to fall into a sin pattern because we become accustomed to the way things are done around us. We need to support those around us and be willing to be accountable to them as well.
When the young Christian church spent time together, they offered support and help to those in need. They shared all they had. They ate and worshiped together, sometimes in private homes as well as the temple. But they were committed to seeing to the needs of their community. 'They devoted themselves to the apostles' teaching and to the fellowship,' (Acts 2:42a) They worshiped openly together while they could.
The time came when the Jewish leadership made it dangerous to worship but they still found a way to serve the Lord. Their fellowship gave them the strength to stand up to the authorities in defense of the Lord. The Lord Jesus told them where 'two or three are gathered together', He is there. When we assemble today to worship Him, serve Him, or do the work of the church, He is there also.
The building we gather in is called a church but the true Church are the believers who are gathering there. In John 17:23, 24a when Jesus was praying for the believers, He said, "I in them and You in Me. May they be brought to complete unity to let the world know that You sent Me and loved them even as You have loved Me. Father, I want those You have given Me to be with Me where I am,…."
God created us to be in fellowship with Him. He loves us. He sent His Son to walk with us in fellowship. The Holy Spirit dwells within the believers to comfort and guide us. He delights in us. We are loved.