R2: washer connection

thank you to Jon, Charlie, Oren, Bob. The extra pipe is 4 feet above ground, same level as cold water inlet and hot water inlet faucet. It is located exactly between cold and hot, same pipe size as cold and hot, but without faucet, just a pipe stick out perpendicular to the wall. It could be anti-hammer, it could be for water softener. My washer I am trying to connect have only cold and hot water hoses and drain. What do I need to do about this pipe? Leave it alone? connect it to something? to what? One possibility is to have a rubber hose and a screw clamp direct it to the drain?
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