Vaka Jātaka (No.300)
A wolf once lived on a rock near the Gaṅgā. The winter floods came and surrounded the rock, and the wolf, unable to escape, decided to keep the holy day. The Bodhisatta, who was Sakka, appeared before him in the guise of a ram, and the wolf, forgetting his holy day, chased him round and round the rock. Finding he could not succeed in catching him, the wolf expressed his joy that his holy day had not been violated! Sakka, hovering above him, rebuked him for his weakness.
The story was related in reference to some monks, followers of Upasena Vaṅgantaputta (q.v.) Being aware of the permission granted by the Buddha to the monks who practiced the thirteen ascetic practices (dhutaṅga) to visit him even during his periods of solitude, these monks would practice them for a short while and then visit him. However, the visit over, they would at once throw off their rag robes and don other garments. The Buddha discovered this and related the Jātaka. J.ii.449 ff; cp. Vin.iii.231 f., where no mention is made of the Jātaka.