摩訶止觀 4.30

4.30

所言「觀心為因緣生法」者，若觀一念心從惡緣起，即能破根本乃至破不雜戒，與善相違，故名為惡。今以善順之心防止惡心，能令根本乃至不雜等戒善順成就，得無毀損，故稱善心，名為防止。惡心既止，身口亦然。防即是止善；順即是行善，行善即是觀；止善即是止。是名「觀因緣所生心持四種戒」也。

What is meant by 'contemplating the mind as a phenomenon produced by causes and conditions'? If one contemplates that a single thought-moment arises from evil conditions, it can destroy the root precepts and even the unmixed precept; being contrary to the good, it is called evil. Now, by using a mind of wholesome compliance to guard against and halt the evil mind, one can bring the root precepts up to the unmixed precept to wholesome, compliant fulfillment without breakage or damage; hence it is called a wholesome mind, termed 'guarding and halting'. Once the evil mind is halted, body and speech are likewise. Guarding against is calming the good; complying is practicing the good. Practicing the good is contemplation; calming the good is calming. This is called 'contemplating the mind produced by causes and conditions to uphold the four kinds of precepts'.