Do not be slothful in zeal, be fervent in spirit, serve the Lord. —Romans 12:11 ESV
Each of these two statements clarifies and protects the other from misunderstanding. “Do not be slothful in zeal”—do not be lazy in zeal—could be taken to mean: be pragmatic. Work, work, work, and don’t worry about your emotions or how you feel. Getting things done is what matters. Be eager and earnest and zealous to get things done. Laziness is the great vice. The great virtue is efficiency and hard work.
But we can see how lopsided that is when we take the positive, clarifying counterpart, namely, “be fervent in spirit.” The word “fervent” comes from the Latin fervens which means “boiling.” That is exactly what this word means in the original Greek (zeontes): boiling—in spirit. So the idea is clearly not one of mere hard work or efficiency. The spirit is in view, not just the body. Feeling is in view, not just doing. So the point of both clauses together is: Don’t just do lots, feel lots.
And it works the other way around. If you read only the second exhortation: “Be fervent in spirit,” you might conclude: The Christian life is one of heart passion. Doing and efficiency are not crucial. Feeling—fervency, boiling in spirit—that is what matters. But that will not do. The first exhortation keeps us from that lopsided view: Not just feel lots, but also do lots.
When it comes to serving Christ, half-heartedness, lukewarmness, laziness, sluggishness, and slothfulness are utterly inappropriate.