Sunakha Jātaka (No.242)
There was in Bārāṇasī a man who owned a dog that had been fattened on rice. A villager saw the dog, and, having bought it from its master, took it away on a lead. Arrived at the edge of the forest, he entered a hut, tied up the dog, and lay down to sleep. The Bodhisatta, seeing the dog, asked him why he did not bite through the lead and escape.
“I am going to,” answered the dog, “as soon as all are asleep.” And he did so.
The story was told in reference to a dog belonging to a water carrier who used to be fed near the Ambalakoṭṭhaka in Jetavana. Once a villager saw it and bought it from the water carrier and took it away on a chain. The dog followed quietly, and the man, thinking it to be fond of him, let it loose. The dog ran away and returned to its old home. The two dogs were identical. J.ii.246‑8.