"Charity -- giving to the poor--is an essential part of Christian morality...I do not believe one can settle how much we ought to give. I am afraid the only safe rule is to give more than we can spare. In other words, if our expenditure on comforts, luxuries, amusements, etc., is up to the same standard common among those with the same income as our own, we are probably giving away too little. If our charities do not at all pinch or hamper us, I should say they are too small There ought to be things we should like to do and cannot do because our charitable expenditure excludes them."
Mere Christianity, book III, chapter 3, paragraph 7 pp. 81-82.
As quoted from The Quotable Lewis, published by Martindale & Root.
Recently I was reminded of this quote as I visited the Cabela's store in Dundee, Michigan. I walked out of there without making a purchase.