49:12 O ye who believe! avoid suspicion as much (as possible): for suspicion in some cases is a sin: and spy not on each other nor speak ill of each other behind their backs. Would any of you like to eat the flesh of his dead brother? Nay ye would abhor it...but fear Allah: for Allah is Oft-Returning Most Merciful.
When one of you yawns they should place their hand over his mouth. (Muslim)