Read Acts 2:41-47.

Growth in Fellowship
“And they continued stedfastly in the apostles' doctrine and
fellowship, and in breaking of bread, and in prayers” (v. 42).

Some years ago, I was sitting on the platform of a church in LaPaz, Bolivia, where I was to preach. During the service, a woman stood to testify. As she did so, there were tears streaming down her face as she spoke with passion. I suddenly felt a wonderful kindred spirit with her. I asked my missionary friend what she was saying. He told me that she said she knew she was saved but was earnestly seeking the blessing of entire sanctification. Later, as I reflected on the “oneness” I had felt, I realized there was little I had in common with her. She was of a different nationality, culture, and language. We lived in different worlds. The only thing we had in common was the one thing that mattered more than all else: the bond of the Holy Spirit, which made me inwardly exclaim, “She is truly my precious sister in Christ!”
The Greek word for this “oneness in Christ” is “koinonia” which is translated “fellowship.” It is a beautiful word that implies communion and communication in the unique relationship that exists between true believers. However, such relationships need to be and should be carefully nurtured by transparency, kindness, and love. (Michael Williams)
“How good and how pleasant it is for brethren to dwell together in unity!”
(Psalm 133:1)