Sri Hayagriva is one of the patron gods of knowledge – the others being Saraswati, Dakshinamurti and Ganesha.

In iconography the horse’s head is indicative of speed, strength, intelligence and the crescent moon is indicative of the mind. This is why it is also to be found on the head of Shiva.

The story of Vishnu’s decapitation is first found in the Shatapatha Brahmana 14 Kanda 1st Chapter 1st Brahmana.

Once the gods Agni, Indra, Soma, Makha, Vishnu and the Vishvedevas went to Kurukshetra to perform a yajña. They agreed that the one who finished first would be elected the superior among them.

Vishnu finished first and was thus entitled to be declared the most excellent among the gods and the yajña-puruṣa – the embodiment of the yajña.

But Vishnu was filled with hubris at his win which annoyed the other gods. He stepped forward and stood holding three arrows and resting his head on the tip of his bow.

The ants asked the gods what would be their reward if they chewed through the bowstring – the gods promised them that they would always find food and water even in a desert.

The ants chewed through the bowstring and the bow sprung straight with the string decapitating Vishnu. His head fell on the ground and became the clay pot called the Mahavira used during yajñas to boil milk.

This story is retold in the Puranas with some differences – the seven sages once visited Amaravati the paradise of Indra and saw Vishnu sitting beside Indra on the throne (In the Rig Veda Vishnu is known as the best friend of Indra – both later take births together – Vishnu becomes Krishna and Indra becomes Arjuna and they remain best friends.)

The sages praised Vishnu as the greatest of all the gods – which really annoyed them and they decided to kill him.

Once they found Vishnu in deep contemplation resting his chin on the tip of his bow. The gods became ants and chewed through the bow string, the bow straightened up with such force it cut off Vishnu’s head, with Vishnu gone the Asuras stole the Vedas.

Saraswati cursed the gods for their evil act, and they repented of their sin because they had lost their protector, so they decided to restore him to life. They found the body, but the head had shot off into the sky to become one with the Sun. Indra then instructed them to bring the head of the first animal they came across which was a horse.

The devas connected the horse’s head to the body of Vishnu and resurrected him and thus was born Hayagriva who pursued the Asuras and defeated them and restored the Vedas to Saraswati who accepted Hayagriva as her guardian and thus he became a partner in the cosmic portfolio of knowledge.