Because thou art lukewarm,
and neither cold nor hot,
I will spue thee out of my mouth.
–Revelation 3:16 (KJV)–

As lukewarm water turns the stomach, and provokes to a vomit, lukewarm professors turn the heart of Christ against them. He is sick of them…They may call their lukewarmness charity, meekness, moderation…it is nauseous to Christ.
–Matthew Henry–