"Therefore, as we have opportunity, let us do good to all people, especially to those who belong to the family of believers"
If you are born again in Christ, then you are in a family of God! You have said that God is your father and that Jesus is your brother. That the church is your brothers and sisters. You have joined a family that is large and unlike any other! No one can say to you, "Get out" or "You don't belong here" and if they do, then they are not speaking from the heart of God.
I have been to a church where they thought that you have to be exactly like them to be part of the church and felt the cold shoulder. I never wish that on another. Thank goodness though I have found a church that doesn't say come when you match what we say is the right way.
Today, I was reminded to be part of a family you must associate with the family. This came in three forms, first a luncheon with church members, then a birthday party with my best friend for her sons, and third a dessert social with the church. Each one was with different people, but each one was important.
The key to connecting with God's people and building a foundation in God, is being where the people are and participating in the life of others. When you let God's people in, you connect to the family and therefor build more of a foundation that will help you stay in the body aka family of Christ.