This particular message comes not from any episode of the series, but from The Simpsons Movie, and could really be a commandment posted at your local movie theatre at this point. Alongside "Thou Shalt Not Talk Through The Picture" and "Thou Must Not Let Thine Brats Kick The Seats In Front Of Them!" Actually, those work just as well at Church. There was actually a second marquee message posted in the movie, which read simply: We Told You So