Om Namah Shivaya is a mantra in Hinduism which is also known as Panchakshara. This mantra consists of five syllables Na Ma Si Va Ya in which Na stands for the Lord’s grace, Ma represents the world, Śi for Śiva, Va stands for His revealing grace, the last syllable Ya represents the soul. Moreover, these five syllables represents the five elements in the world such as Na for earth, Ma is water, Śi stands for fire, Vā is air, and Ya stands for Akasa.
Now coming to the question Why should a devotee chant Om Namah Shivaya?. According to Hinduism, Shiva is the God of destruction and hence is very powerful. We chant the mantra Om Namah Sivaya, because the advantages are unlimited.
Through chanting this mantra, you get peace of mind and access concentration that makes you forget about the outside world when you are chanting the mantra. As per Hinduism, there is a belief that a person who recites this mantra will get longer life, because Shiva , the God of destruction will be pleased by your religious mind and spare you to live on this earth for a longer period.
Apart from the spiritual side of the advantages of chanting this mantra, there are many benefits that are physical which you stand to gain through reciting this mantra. For chanting this mantra, you need to take a deep breath which in turn pumps more air to your lungs and thereby the blood is facilitated to get more oxygen and purify the blood.
The more oxygen to the whole body means the body remains healthy. While chanting the mantra, you are required to maintain the right posture i.e. sitting erect and this helps your spinal cord and muscles accessing more strength and thus leading to a good physique. Hence, chanting the mantra NAMASIVAYA offers one both spiritual as well as physical well being.