天台四教儀 1.78

1.78

Fifth is recognizing the open and the blocked: suffering and origination, the twelve links of dependent origination, the six obscurations, [the delusions of] dust and sand, and ignorance are the blocked; the path and cessation, the wisdom of the cessation of dependent origination, the six perfections, and the three contemplations in one mind are the open. If something is open, it must be protected; if there is a blockage, it must be dismantled. If a blockage arises within the open, what can dismantle is like what is dismantled, examining and checking at every juncture—this is called recognizing the open and the blocked. The sutra says: "Red cushions were arranged [outside the carriage]."