When you are laboring for others let it be with the same zeal as if it were for yourself.
Confucius
Zeal is a volcano, the peak of which the grass of indecisiveness does not grow.
Khalil Gibran
Zeal will do more than knowledge.
William Hazlitt
Spiritual infirmities such as tepidity are caused, not only by chills but also by fevers, that is, by excessive zeal.
Saint Ignatius
When suave politeness, tempering bigot zeal, corrected 'I believe' to 'one does feel'.
Ronald Knox