Generally the sages/ sadhgurus/ incarnations of God do the service at the highest level unconditionally ….it’s the LOVE and they are devoted. In this context the important thing is:
They emptied their vessels to fill with anything. They leave everything to receive anything.
We may not fill the overflowing glass with new water, to fill it with new we have to empty it. Those are the persons who empty everything even the marks of water and ready to receive and fill any new thing. They can give you anything you want because they can receive anything but keeps nothing for them.
Let us dare to dream to become like those highest personalities.