The context is the next sentence. "do not let your left hand know what your right hand is doing, so that your giving may be in secret." It's just hyperbolic/p

The context is the next sentence. "do not let your left hand know what your right hand is doing, so that your giving may be in secret." It's just hyperbolic/poetic language. It's not possible to do something in such a way that your right hand doesn't know what your left hand is doing, because they are both connected centrally (and they can't know anything to begin with). "Be so secretive that your resting hand doesn't know what your charitable hand is doing."