Thought from Medical Science
It has been stated in medical science that physical unfitness and due to that problems and tensions are always occurring in human life. To get rid from these tensions and problems Lord Shiva and Vishnu are being prayed. In the same manner the Narayan Nagbali vidhi is to be performed is stated in medical science. Ayurveda or one of the four Ved which deals with medical sciences having thoughts of Jivatma i.e. a living soul. Ayurveda is a sub part of Atharvaved. In Ayurveda decease, reason for decease, health and source of decease has been discussed. Ayurveda has studied various methods of Etiology. One of the methods is called as "Karmaj. This method has been included in "Ashtang Ayurveda".
This has been crystal clear from the above said verse that if there i etiology of decease and a suitable treatment that has been given but sti a decease is not getting cured the type of decease is called a "Karmaj". A proper etiology, medical treatment should be supported with strong divine power. If all this combine then decease will surely be cured. Anger of Lord Shiva is the source of decease's like fever. To get rid from this decease worship of Lord Shiva is suggested in medical science i.e. sin from a human being is the source of its own. This type of decease’s is not getting cured and exists forever till the sins which are the source of decease got cleaned. A decease which is the product of sin is may be due to killing of a Brahmin i.e. Bramha-hatya, killing of a women i.e. Stri-hatya, a stolen asset or from the funds who belongs to others. These all sins will be cured only by the divine power or through the worship of Gods. This has been mentioned in "Sushruf" grantha i.e. holy book that, to get rid of mental decease's Lord Shiva with his army specially called as "Gana" is to be prayed. This is the main part of Narayan Nagbali vidhi. Bhagwan dhanvantari who is also God of medical science is mentioned.
This Narayan Nagbali vidhi may be performed about any person, from any cast. A person whose parents are alive can also perform vidhi. A bachelor who is from Brahmin cast and having Janava (Sacrificial thread) can also perform this vidhi This vidhi is to be performed by a couple for getting an issue. The person who is unmarried or widower can also perform this vidhi. If some ones wife is pregnant then up to 5th month this vidhi can be performed. If there is a wedding or ceremony of issuing a sacrificial thread is happened then after one year of this ceremony this vidhi of Narayan Nagbali may be performed.