This is a good article by sadguru jaggi vasudev on why we apply vibhuti
There are many aspects to the usage of vibhuti or sacred ash. First of all, it is a great medium to transfer or transmit energy, and it has an ability to help direct and control the energy body. Apart from that, there is a symbolic significance to applying vibhuti on the body. It is a constant reminder of the mortal nature of life – it is like you are always wearing mortality on your body.
Normally, yogis use the ash that they pick up from the cremation grounds. If this ash cannot be used, the next alternative is to use cow dung. There are other substances used but the basic material, the body of it, is cow dung. If even this ash cannot be used, the next alternative is to make vibhuti of rice husk. This is indicative that the body is not the core substance, it is just the husk.
Unfortunately, in many places it has become a scandalous business where they are just giving a certain white rock powder as vibhuti. But if vibhuti is properly prepared, and if you know where and how to apply it, it makes you much more receptive, and the place where you apply vibhuti on your body becomes more sensitive. The sensitivity gets more subtle and goes towards the higher nature. So, before you step out of the house in the morning, you apply vibhuti at certain points to receive the divine around you, not the devil. Depending on which aspect of you is receptive at that moment, you can receive life in different ways and from various dimensions of who you are. You must have observed this – at one time, you saw something and experienced it in a certain way. Some other time, you saw the same thing and experienced it in a totally different way. The way you receive life makes the difference. So, you want the higher aspects of you to be receptive, not the lower.
Within your physical body, there are seven basic centers representing seven dimensions of experiencing life. These centers are known as chakras. A chakra is a certain meeting point within the energy system. These chakras are not physical, they are of a subtle nature. One can experientially know these chakras, but if you cut the body and see, you will not find any chakra. As you move into higher levels of intensity, naturally the energies will rise from one chakra to another. If you receive life from the higher chakras, the same situation will be different for you than if you receive life from the lower chakras.
How Should We Apply Vibhuti?
Traditionally, vibhuti is taken between your thumb and your ring finger – you don’t have to pick up a lot of it, just a little bit – and applied between the eyebrows, known as the agna chakra, at the pit of the throat known as the vishuddhi chakra, and in the center of the chest where the ribcage meets, known as the anahata chakra. It used to be common knowledge in India that you must apply vibhuti at these points. The reason why these particular points have been specified is because vibhuti makes them more sensitive.
Vibhuti is usually applied at the anahata so that you receive life as love. It is applied at the vishuddhi so that you receive life as power; power does not mean just physical or mental power, there are so many ways in which a human being can be powerful. The idea is to make the life energies very strong and powerful so that your very presence has an influence on life around you – you don’t have to speak or act – if you simply sit, you influence the situation around you. This kind of power can be developed within a human being. Vibhuti is applied at the agna so that you receive life as knowledge.
This is a very deep science, but today, without understanding the science behind it, we simply apply vibhuti like a stripe on the forehead. The one who has stripes one way does not agree with the one who has the stripes another way – this is stupidity. Vibhuti is not something that Shiva gave, or this or that god gave. This is not a question of belief. In this culture, it has been looked at deeply as a tool for a person’s growth. Properly prepared vibhuti has a different vibrancy. There is a need to revive and make use of the science behind this.