Craig

“A zealous man in religion is pre-eminently a man of one thing. It is not enough to say that he is earnest, hearty, uncompromising, thorough-going, whole-hearted, fervent in spirit. He sees one thing, he cares for one thing, he lives for one thing, he is swallowed-up in one thing — and that one thing is to please God. Whether he lives — or whether he dies; whether he has health — or whether he has sickness; whether he is rich — or whether he is poor; whether he pleases man — or whether he gives offence; whether he is thought wise — or whether he is thought foolish; whether he gets blame — or whether he gets praise; whether he gets honor, or whether he gets shame — for all this the zealous man cares nothing at all. He burns for one thing — and that one thing is to please God, and to advance God's glory. If he is consumed in the very burning — he is content. He feels that, like a lamp, he is made to burn, and if consumed in burning — he has but done the work for which God appointed him. Such a one will always find a sphere for his zeal. If he cannot preach, and work, and give money — he will cry, and sigh, and pray. Yes, if he is only a pauper, on a perpetual bed of sickness — he will make the wheels of sin around him drive heavily, by continually interceding against it. If he cannot fight in the valley with Joshua — then he will do the prayer-work of Moses, Aaron, and Hur, on the hill. (Exod. 17:9-13.) If he is cut off from working himself — he will give the Lord no rest until help is raised up from another quarter, and the work is done. This is what I mean when I speak of "zeal" in religion.”
― J.C. Ryle