What was the specific promise Babasaheb Tarkhad made to his son that convinced him to travel to Shirdi?

To convince his son to accompany his mother to Shirdi, Babasaheb Tarkhad had to agree to a strict condition. As detailed in Chapter 9, the son insisted that no one in the household should consume food until a 'Naivedya' (food offering) was first made to Sai Baba. Babasaheb Tarkhad gave his word, assuring his son, "Go, I will offer Naivedya daily; be certain." He further promised, "Without first dedicating to Sai, no one will consume food. Take this word of mine as proof; do not doubt, go in peace." Upon receiving this firm assurance, the son finally agreed to make the journey.