The original mind flows like water and does not stay in one spot, while the deluded mind is like ice. You cannot wash your hands and feet with ice. But if you melt the ice and turn it into water, then it can flow everywhere and you can wash your hands and feet and everything with it.
When the mind stays in one spot and clings to anything; it is like ice and cannot be used freely, just as you cannot wash hands and feet with ice. To melt the mind and to let it work, like flowing water, in every part of the body—that is what is meant by “original mind.”