3:16 `So because you are lukewarm, and neither hot not cold, I will spit you out of My mouth.

So because you are lukewarm and neither HOT nor COLD,

A lukewarm church is the worst kind. If it is COLD, it won't harm anyone. If it is HOT, the people are alive and spiritual rebirth is happening.

But a TEPID church

A church that is "lukewarm" invites false teachings to invade. 2 Peter 2:1-3; 2 Peter 2:18-19; and 2 Timothy 3:1-5. Note: the lukewarm church has a judgment coming:

I will spit you OUT OF MY MOUTH!

Praise the Lord, the tense on the verb is 'will', future. There still is time to repent and to be renewed. According to 1 Peter 4:17-19, the church first is judged, then fakes ('godless men') within the church, and lastly sinners.