The Original Face by Daito Kokushi
National Teacher Daito (1283-1338) explains that Zen training is about realising our 'Original Face' before father and mother were born. In less than five minutes he explains not only the 'why' but succinctly 'how' to do this...
Daito Kokushi's sermon on The Original Face from 'A First Zen Reader' translated and complied by Trevor Leggett.
The Original Face - A Sermon by Daito Kokushi