It is said in Bhagavad Geeta, that we should live our life according to scriptural injunctions. What scriptures should we follow exactly? Where are the regulated principles laid out?
I will answer according to Kashmiri Shaivism because the teachings of Bhagvat Geeta are meant to unite individual consciousness to the universal consciousness which is the ultimate aim in Kashmiri Shaivism (is to unite with Śiva/universe - Shivvyāpti.) This is said in Virupākshapañchākshikā.
Indeed, in the writings of the sages Shuka, Vamadeva, Krishna, Dadhici, and Vainya, identity with the universe is explained to be born of the yoga of identification with the elements. ( Verse 50)
So, any scripture which are meant to unite individual consciousness to universal consciousness should be followed. i.e Shāstras teaching the methods & philosophy to unite with the ultimate reality.
One may read Bhagvat Geeta & Upanishads with non dual commentaries to understand non duality which is prerequisite to unite individual consciousness to the universal consciousness. But I will cite scriptures of Kashmiri Shaivism as I'm answering according to Kashmiri Shaivism. Kashmiri Shaiva scriptures are broadly classified as
- Pratyabijna Shāstras - teaches philosophy of Pratyabijna. Non dualism between Shiva & Añu. Pratyabijna Hridyam, Ishvar Pratyabijna, Shiv drishti, Tantrāloka, tantrasāra etc are some Pratyabijna Shāstras.
- Spanda Shāstras - Expands content of Shiv Sutras from the point of Shakti. E.g, Spanda Karika or Spanda Sutras.
- Āgama Shāstras - Revelation of Shiva. They lay down both principles & practices. E.g, Mālinivijay tantra, Svechcandra tantra, Vijnānabhairav tantra, Rudrayāmala tantra, Shiv Sutras etc.
Summary verse by achārya Abhinavgupta in his commentary on Bhagvat Geeta.
That all merciful Parāshakti, which blesses all living beings, blossoms & expands in that unitary consciousness called Brahman; therefore, one should strive to attain that highest reality.