Who Mitra is
Mitra is the friend among the Vedic gods. His name is the ordinary word for a friend, and it is also an old word for an agreement between two people. He is the god who stands behind both.
He is hardly ever praised alone. The Rigveda has more than twenty hymns to the pair Mitra-Varuna and only one, hymn 59 of the third book, to Mitra by himself. In the paired hymns the two are kings who keep the order of the world. They see everything, and the sun is called their eye. Whoever breaks his word has to answer to them.
The one hymn that is Mitra's own is short and calm. It says that when Mitra speaks, people stir and set to their work. He holds up the earth and the sky. He watches the people with eyes that never close. The man who keeps Mitra's law is not killed or conquered, and trouble does not reach him from near or far. The five peoples have all come to him, the hymn says, and he sustains all the gods.
Scholars have noticed one word in that hymn that belongs to Mitra more than to anyone else. He is the one who brings people together, who gets them moving in one direction. The same is said of the fire god, who is called Mitra when he is kindled.
His name is very old. A treaty of the fourteenth century before the common era, made by a king of Mitanni in western Asia, calls on Mitra, Varuna, Indra and the Nasatyas to witness the oath. In ancient Iran the same god is Mithra, guardian of the given word and close companion of the sun.
In the Vedic texts that follow the Rigveda, the pair is divided between light and dark. The Atharvaveda sets Mitra at sunrise and Varuna in the evening. A Yajurveda text says that Mitra brought forth the day and Varuna the night. In the ritual a white animal is offered to Mitra and a dark one to Varuna.
There is very little story about him. The one tale that is his own shows him refusing to take part in a killing, because he is the friend of all.
When Mitra speaks, people rise and go to their work. He holds up the earth and the sky, and he watches over the people without closing his eyes.