Siman 187

(3.) Before he left Breslov for Uman to pass on there — at the time he left the doorway of the house and outside to ascend upon the wagon — he stood by the mezuzah and placed his hand upon the mezuzah. He answered and said to the world: "See to it that you all gather together and pray together — for if you pray with intention, perhaps you will be able to draw me back here once more."