Under normal circumstances there is no reason to wash buds, plus you risk mold/rot. To quote danceswithweeds above:
"Just like lettuces and spinach that grow right down at the ground where the farmer has spread last year manure for fertilizer. You know? Just the nitrogen you put on your plants come from chicken manure, mostly. You do foliar and spray that stuff into the leafs and bud and I've been hearing that indoor growers don't wash their bud. If that stuff is on your bud when you go to smoke it you are literately smoking chicken shit."
Plus when you eat most produce, hot dogs, a lot of different foods you're eating bugs, shit, rat hair etc. Unless a bird shit on your buds there is no reason to wash them