first sermon 

The Buddha's first sermon delivered at the Deer Park, known in the commentaries as the Dhamma-cakkappavattana Sutta (Pāli) or Dharma-cakra-pravartana Sūtra (Sanskrit), meaning ‘The Discourse of Setting in Motion the Wheel of the Law’. In this discourse the Buddha sets out the basis principle of the middle way (madhyamā-pratipad), and the teaching of the Four Noble Truths. It was said to be delivered on the full-moon night of the month of Āsāḷha.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)