Can you tell me a story about how Sai Baba kept his promise to a devotee?

Yes, there is a wonderful account in Chapter 40 about a devotee named Dev who was holding an Udyapan ceremony. Dev invited Baba, who promised, "I am coming." Though Dev did not see Baba in his familiar form, Baba did attend the feast. He later revealed through another devotee, Jog, that he had come in the guise of a Sanyasi accompanied by two others. Baba emphasized his commitment to his word, stating, "for the sake of My word, I would die; but the words from My mouth shall never be otherwise." This story beautifully illustrates how Baba fulfilled his promise, even when his devotee initially failed to recognize him in a different form.