UDI It is well-known that Baba took Dakshina from all, and out of the amount thus collected, He spent a lot on charity and purchased fuel with the balance left with Him. This fuel He threw in the Dhuni - the sacred fire, which he kept burning. The ash from this fire was called Udi and it was freely distributed to the devotees at the time of their departure from Shirdi. Udi or ash is the purest substance on earth having tremendous powers of doing and undoing and is the result of sacrifices offered to fire (agni) which purifies everything by destroying whatever is evil. Performing 'Yagha' (Dhuni) is the most pious ritual recommended in the ancient Vedic literature.
There is a deeper underlying significance behind Baba’s practice of distributing Udi. Baba taught by his udi that all the visible phenomena in the universe are as transient as the ash. Our bodies composed of wood or matter of the five elements will fall down, become inanimate after all their enjoyments are over, and will be reduced to ashes. In order to remind the devotees of the fact that their bodies will be reduced to ashes, Baba distributed Udi to them. Baba also taught by the Udi that the Brahma is the only reality and the universe is ephemeral and that no one in this world, be he a son, father or wife, is really ours. We come here (in this world) alone and we have to go out alone. It was found and is even now found out, that the Udi cured many physical and mental maladies, but Baba wanted to din into the devotee's ears the principles of discrimination between the Unreal and the Real, non-attachment for the unreal, by His Udi and Dakshina. The former (Udi) taught us discrimination and the latter (Dakshina) taught us non-attachment. Unless we have these two things, it is not possible for us to cross over the sea of mundane existence. So Baba asked for and took Dakshina, and while the devotees took leave, He gave Udi as Prasad, besmeared some of it on the Bhaktas' foreheads and placed his boon-conferring hand on their heads. When Baba was in a cheerful mood, he used to sing merrily. One such song was about Udi. The text of the Udi song was, 'Oh, playful Rama, come, come, and bring with you sacks of Udi.' Baba used to sing in very clear and sweet tones.
So much about the spiritual implication of Udi. It also had its material significance. It conferred health, prosperity, freedom from anxiety, and many other worldly gains. So the Udi has helped us to gain both our ends - material as well as spiritual.