Minecraft wiki entry for Defeating_the_wither, associated text: A tactic that is relatively easy to pull off is to dig down near bedrock, and dig a long 1×2 tunnel (longer than 30 blocks). At the end of the tunnel, construct a small room. Spawn the wither in this room, then run back into the tunnel. Occasionally pop out and shoot an arrow or two at the Wither. As the Wither crunches its way toward the player, just walk backward through the tunnel. Once the wither has reached its "armor" stage, jump out and begin hitting it with a diamond sword. As long as the player frequently throws down splash potions of instant healing, the player should be able to survive even with iron armor.