Legend of Ardhanarishvara
Sage Bringi was one of the ardent followers of Lord Shiva. He used to worship only Lord Shiva but not Shakti. Goddess Shakti, being the power of the universe pulled out the energy from Bringi Maharishi's body. Now he was even unable to stand. The sage then pleaded to god. God Shiva provided him with a stick.
The Rishi could walk with the support of the stick and continued worshipping Lord Shiva alone. Goddess Shakti wanted to become an inseparable part of Lord Shiva. She started observing Kedara Mahavrata austerity, which is also known as Deepavali. Lord Shiva was propitiated with the austerity and granted her boon of being part to his own form. The Lord thus became Ardhanarishvara.
This is one of the very important forms of the god worshipped by Hindus. The reference of Ardhanarishvara is found in many Hindu scriptures. God is beyond the concept of any sex. So God can be male, female, and even neuter too. So god exists in intrinsic condition as is referred by Ardhanarishvara.
Philosophically this form is quite associated with the grace of God. The formless god is called Parashiva. The god creates the world and act for the benefits of Pashus (souls), who are attached by Pasha (bondage). The power of creation comes from Shiva and Shakti. Though they are incorporated in the same form they act independently as well as jointly. This is understood when the philosophers in ancient scriptures describe Shakti as wife, mother and daughter of Shiva. As wife, Shakti acts together with Shiva, as mother Shakti becomes Shiva or Shiva comes out of Shakti and as daughter Shiva becomes Shakti.
India from its ancient time has many sculptures and paintings of Ardhanarishvara, which are found in various poses, like 'Abhanga', a posture with only one curve, 'Tribhanga', a posture with mild three curves and 'Atibhanga', a posture with extreme curves. Thus maleness and femaleness are contained in one frame in Ardhanarishvara.
Symbolism of Ardhanarishvara
Ardhanarishvara symbolizes male and female principles cannot be separated. It conveys the unity of opposites in the universe. The male half stands for Purusha and female half is Prakriti. The union of Purusha (Shiva) and Prakriti (Shiva's energy, Shakti) generates the universe. Mahabharata lauds this form as the source of creation. Ardhanarishvara harmonizes the two conflicting ways of life: the spiritual way of the ascetic as represented by Shiva, and the materialistic way of the householder symbolized by Parvati. It conveys that Shiva and Shakti are one and the same.