The Simpsons S13 E06 She of Little Faith

"Just a product of society that's lost its good manners."

After Homer and Bart's model rocket damages the church, Mr. Burns makes a deal to commercialize the church in return for paying for the damages. Lisa becomes disgusted at what the church has become, so she decides to find a new religion suitable for her. She eventually converts to Buddhism, causing Marge to fear for Lisa's soul.