You might have seen a government-required sign at a McDonald's restroom telling employees to wash their hands. Muslims do this as a part of living their faith, which is called sharia in Arabic. The Prophet Muhammad also encouraged Muslims to wash their hands before and after eating. Muslim parents raise their children on many such manners. The first chapter in almost all books on sharia is about morals and manners of cleanliness, which Prophet Muhammad said is half of the faith. God's peace and blessings be upon him.
When Muslims begin anything they say, "in the name of God." -- that is sharia. When they greet each other, they smile and say, "Assalamu Alaikum" (peace be with you) -- that is sharia. (More)