The twelfth sutta of the Mahā Vagga of the Suttanipāta.

A dissertation delivered by the Buddha, outside the Migārāmātupāsāda, on a full-moon day. He tells of the twofold insight — the insight into suffering (dukkha) and its cause, and the insight into its cessation (nirodha) and the path leading to its cessation. He proceeds to explain the origin of suffering from the substratum of existence (upadhi), ignorance (avijjā), mental formations (saṅkhārā), etc. (SN. p.139 ff).