In many myths, the dog has been a messenger between life and death, between the higher and infernal powers, between the gods and man. For example, the ancient Egyptians worshiped the god Anubis, the judge and lord of the afterlife.
If the dog is a guide to the realm of the dead, it is also a keeper of the boundary between the two worlds. A companion in life, it continues to be such in death and so weaves the two together in a pattern of perpetual coming and going, a continual design of birth, death and rebirth.
Painting by John EmmsIn Christianity, Saint Guinefort, who was never officially recognized, was a greyhound that received local veneration as a saint after miracles at his grave. In fact, this loyal beast had slain a deadly viper that threatened the infant. In other interesting case, Saint Christopher is said to have come from the dog-headed tribe, where he was a cannibal and a barbarian, until he was redeemed, becoming an ascetic "athelete of God."
And in Hinduism, there are many images of dogs or shvan. The Apsara of Indra is named Sarama, and it is mentioned in the Rig Veda. Its offspring became the watch dog of Yama. Deities like Rudra, Nirriti, Virabhadra, Khandoba and Dattatreya have these companions. And certainly, Shiva, in his aspect as Bhairava, had a dog as a vahana.
"The dog must come with me".
"That is not possible," said Indra, - "All cannot attain heaven. The dog is old and thin and has no value."
"In that case, I do not seek heaven,"- said Yudhisthira, - "The dog was my faithful companion and I cannot abandon it. It sought my help and gave me unconditional love. The pleasures of heaven will mean nothing to me in comparison to its grief. It has done nothing to deserve abandonment and had none of the weaknesses of my wife and brothers. If it does not deserve to go to heaven, then neither do I." And so he turned back.
"Stop!" - cried Indra, - "None have the qualities that you possess, O Yudhisthira! The dog is Dharma, from whom you have descended!" And indeed, the dog had transformed into the God of Dharma and blessed Yudhisthira for his complete lack of selfishness and dedication to righteousness in all circumstances.
So, ask yourself a zen-question "Does a dog have Buddha nature or not?"