Any Ideas?

As I was walking past Escuela de Christo Church this morning, I saw a stone carving above the front door that I'd not noticed before. I have no idea what it says or means. There's a hand holding what appears to be a compass and a large snake. Enlarge it by clicking on the image once or twice. You might even use your browser to enlarge it more. It didn't help me understand what it meant, but maybe you can figure it out.