Is interchurch fellowship voluntary or obligatory?

“Fellowship between churches is voluntary and does not hold authority over any local church. No church can be compelled to attend, contribute, or submit to another body, for each congregation is independent and self-governing under Christ.”

This upholds the New Testament pattern where local churches cooperated freely (e.g., helping with offerings, Acts 11:29–30; 2 Corinthians 8–9) but no external authority forced them.