The Bodhicaryāvatāra is the classical work on Mahāyāna Buddhism and was composed in Sanskrit by the Indian monk Śantideva in the 7th century. In ten chapters, Śantideva gives detailed step-by-step instructions of the ethical and psychological training one must undertake to become a bodhisattva. The Bodhicaryāvatāra was widely used as a text book in ancient India and later had, and continues to have, enormous importance in Tibet.
Santideva - The Bodhicaryavatara, trans. by Kate Crosby and Andrew Skilton, 1995.