What exactly was the promise Babasaheb Tarkhad made to his son, and how did he end up breaking it?

The promise Babasaheb Tarkhad made is explicitly stated in Chapter 9. To convince his hesitant son to travel to Shirdi, he gave his word, saying, "Without offering Naivedya to Sai, no one should consume food at home." He assured his son he would personally perform the daily worship. The Naivedya he offered was a piece of sugar candy. He broke this promise one day when his mind was busy with his business as a chief officer of a large mill. In his preoccupation, he completely forgot to offer the sugar candy during the morning worship. The mistake was only realized later when the entire household had already finished their meals for the day.