But as the believers rapidly multiplied, there were rumblings of discontent. Acts 6:1
Have you heard people grumble and complain in your church?
I have!
I’ll tell you up front – it’s a sign of immaturity in a Christian.
You may think that if something is wrong then people have a right to complain. If something is wrong people have a right to pray and talk about it – not grumble and complain, which to me is going behind everyone’s back and gossiping about the problem.

What does the Bible say about problems?
“If another believer sins against you, go privately and point out the offense. If the other person listens and confesses it, you have won that person back. But if you are unsuccessful, take one or two others with you and go back again, so that everything you say may be confirmed by two or three witnesses. If the person still refuses to listen, take your case to the church.” Matt 18:15-17
Problems and personal conflicts should be kept low-key and not become a church wide problem unless absolutely necessary.
However it must be dealt with or it will eventually fester into a church wide problem.

This is what happened to the church in Acts 6. More believers gave opportunity to more problems and complaining to arise. Instead of someone going to someone and saying, “We have a problem. Can we work this out?” the problem became a rumbling of discontent from one group against another.
It became an instant church wide problem that caused the apostolic leadership to stop ministering the word and handle the situation.

Do everything without complaining and arguing. Phil 2:14
These people are grumblers and complainers, living only to satisfy their desires. They brag loudly about themselves, and they flatter others to get what they want. Jude 16
Don’t grumble about each other, brothers and sisters, or you will be judged. James 5:9