‘Vibhuti Abhishekam’, the worship of the silver idol of Shirdi Sai Baba with vibhuti, was associated with the Sivarathri festival. It used to be performed by Bhagawan Himself. Howard Murphet, who witnessed this astounding spectacle during the Sivarathri celebrations in February 1966 describes it in his book, “Sai Baba – The Man of Miracles":

"On the stage is a large silver statue of Sai Baba of Shirdi in His characteristic sitting posture. Mr. Kasturi takes up a small wooden urn, about a foot in height, and filled with Vibhuti. This he holds above the head of the silver statue, and lets the ash pour over the figure until the urn is empty. He shakes it well to make sure that the last grains have fallen out, then continues to hold it above the statue with its open top downwards.

Now Sai Baba thrusts His arm as far as the elbow into the vessel and makes a churning motion with His arm, as women did when making butter in the old days. Immediately the ash begins to flow again from the vessel and continues to do so in a copious stream until He takes His arm out. Then, the flow of ash stops.

Next He puts His other arm in and twirls that around. The ash streams out over the statue again. This process goes on, Baba using alternate arms, ash pouring from the empty vessel while His hand is in it, and stopping as soon as He takes it out. Finally Shirdi Sai is buried in a great mound of ash - much more than the vessel could possibly have held.

Now the urn is placed on the floor: the miraculous, ceremonial ash bath is over. There is a joyous, elevated atmosphere all around; Mr. Kasturi's face is more radiant than ever, Baba's movements and manner are the acme of unselfconscious grace. It's all wonderful, yet having watched Him pull handfuls of ash out of the empty air I am not so greatly surprised to see Him stir it in large quantities from an empty pot.”

Reference: “Sai Baba: Man of Miracles” by Mr. Howard Murphet. Page: 42-43 (Paperback Edition). Published by Macmillan India Ltd, 1972.