"If you've ever made change in the offering plate, you might be a redneck"

This quote by Jeff Foxworthy is an amusing method of stating that if you are from a rural, working-class background, you might be a redneck. The expression "making modification in the offering plate" is a referral to the tradition of circulating a collection plate throughout church services, and putting cash into it. The expression indicates that if you are from a rural, working-class background, you might not have adequate cash to put an entire bill into the plate, so you have to make modification with coins. This quote is a humorous way of saying that if you come from a rural, working-class background, you may be a redneck.