Real generosity is an unfailing sign of spirituality.

Commentary by Hazrat Inayat Khan:

The absence of generosity means that the doors of the heart are closed; nothing from within can come out, and nothing from without can enter in.
Tawazu' in Sufic terms means something more than hospitality. It is laying before one's friend willingly what one has, in other words sharing with one's friend all the good one has in life, and with it, enjoying life better. When this tendency to tawazu' is developed, things that give one joy and pleasure become more enjoyable by sharing with another. This tendency comes from the aristocracy of the heart. It is generosity and even more than generosity. For the limit of generosity is to see another pleased in his pleasure, but to share one's own pleasure with another is greater than generosity. It is a quality which is foreign to a selfish person, and the one who shows this quality is on the path of saintliness.
The spirit of generosity in nature builds a path to God, for generosity is outgoing, is spontaneity; its nature is to make its way toward a wide horizon. Generosity, therefore, may be called charity of heart. It is not necessary that the spirit of generosity be shown always by the spending of money; in every little thing one can show it. Generosity is an attitude a person shows in every little action that he does for people that he comes in contact with in his everyday life. One can show generosity by a smile, by a kind glance, by a warm handshake; by patting the younger soul on the shoulder as a mark of encouragement, of showing appreciation, of expressing affection. Generosity one can show in accommodating one's fellow man, in welcoming him, in bidding farewell to one's friend. In thought, work, and deed, in every manner and form one can show that generous spirit which is the sign of the godly.