The "kind hand" belongs to the Spirit of Christmas Yet to Come, which is showing Ebenezer Scrooge the deserted and neglected grave that is fated to be his after showing him the joy with which many people learned of his death. Scrooge, having understood the lessons delivered by the three Spirits, pleads with the Spirit for some assurance that it is not too late to change the course of events and the eventual outcome of his life.
I am not the man I was. I will not be the man I must have been but for this intercourse. Why show me this, if I am past all hope!
Although the Spirit says nothing, the hand appears "to shake" as Scrooge continues to make his case.
Good Spirit...your nature intercedes for me, and pities me. Assure me that I yet may change these shadows you have shown me, be an altered life?"
The trembling of the Spirit's hand is affirmation that the Spirit does care about Scrooge's destiny and that his fate can be changed from what the Spirit has shown him if he chooses to change his ways.