I have posted a few times about how church marquees often carry messages that the church would not want to communicate. As a whole, I think church marquee messages are usually banal and ridiculous, but sometimes the humor that they carry are worth every penny. See my posts here, here, here, and here for more church signage humor.
In these two church signs (HT to Scotteriology), the humor comes from the figure of speech paronomasia, which is essentially a pun or play on words. I will leave it up to you to figure out the play on words.