While the perfections or Paramitas described in the Jataka tales were originally taken as descriptive, in order to engender reverence for the Buddha, Mahayanists took the Paramitas as prescriptive, as the model we should follow in our own Bodhisattva path to full Buddhahood.
Perhaps the earliest genre of Buddhist literature in which the pāramitās appear are the collections of Jātakas, the stories of the Buddha’s previous lives.
The pāramitās in these stories provide major underlying themes, such as self-sacrifice, ethical virtue, and patience, that demonstrate the magnificent qualities developed by the Buddha in his previous lives by carrying out moral acts as a bodhisattva on the bodhisattva path.
In the Aviṣahya Jātaka, for example, the bodhisattva cultivates the perfection of generosity (dānapāramitā) by donating alms to supplicants in spite of being reduced to poverty. The bodhisattva is a boy who refuses to steal, even after encouragement from his Brahmin teacher to do so, in the Brāhmaṇa Jātaka, to illustrate the cultivation of the perfection of morality (śīlapāramitā). In the Kṣāntivādin Jātaka, the bodhisattva is an ascetic who cultivates the perfection of forbearance (kṣāntipāramitā) by tolerating being violently disfigured by an angry king.5 Most Buddhist groups (nikāya) had collections of Jātakas that differed in length and number.
Buddhist groups and movements also understood the purport of the Jātakas differently, with mainstream groups like the Theravāda seeing the perfections in the Jātakas as qualities to be admired, while Mahāyāna movements understood the perfections in the Jātakas as models to emulate.
http://religion.oxfordre.com/view/10.10 ... 0378-e-193