Mahabharata, Book 5, Section Vउद्योगपर्व

“Krishna said, ‘These worlds are worthy of the chief of the Somaka tribe, and are calculated to promote the interests of Pandu’s son of immeasurable strength. As we are desirous of adopting a politic course, this is, no doubt, our first duty; a man acting otherwise would be a great fool. But our relationship to both the Kurus and the Pandus is equal, howsoever these two parties may behave with each other. Both you and we have been invited here on the occasion of a marriage. The marriage having now been celebrated, let us go home well-pleased. You are the foremost of kings, both in years and learning; and here we all, no doubt are as if your pupils. Dhritarashtra has always entertained a great respect for you; and you are also a friend of the preceptors Drona and Kripa. I, therefore, ask you to send a message (to the Kurus) in the interests of the Pandavas. We all resolve even upon this that you should send a message unto them. If that chief of the Kuru race should make peace on equitable terms, then the brotherly feelings between the Kuras and the Pandus will sustain no injury. If on the other hand, the son of Dhritarashtra should wax haughty and from folly refuse to make peace, then, having summoned others, summon us too. The holder of Gandiva then will be fired with wrath and the dull-headed and wicked Duryodhana, with his partisans and friends, will meet his fate.’"

Vaisampayana said, “King Virata, then having honoured Krishna, sent him home with his followers and relatives. And after Krishna had set out for Dwaraka, Yudhishthira and his followers, with king Virata, began to make preparations for war. And Virata and his relatives sent word to all the monarchs, and king Drupada also did the same. And at the request of those lions of the Kuru race, as also of the two kings of the Matsyas and the Panchalas, many lords of the earth possessed of great strength, came to the place with cheerful hearts. And when the sons of Dhritarashtra heard that the Pandavas had collected a large army, they also assembled many rulers of the earth. And, O king, at that time the whole land became thronged with the rulers of the earth who were marching to espouse the cause of either the Kurus or the Pandavas. And the land was full of military bands composed of four kinds of forces. And from all sides the forces began to pour in. And the goddess Earth with her mountains and forests seemed to tremble beneath their tread. And the king of the Panchalas, having consulted the wishes of Yudhishthira, despatched to the Kurus his own priest, who was old both in years and understanding."