摩訶止觀 2.108

2.108

復次，時節難起，王事所拘，不得修善，令於惡中而習止觀。汝今無難、無拘，何意純用乳藥毒他慧命？故《阿含》中放牛人善知好濟，令牛群安隱。若好濟有難，急不獲已，當從惡濟。惡濟多難，百不全一。汝今無事，幸於好濟，善道驅牛，何為惡道自他沈沒？破壞佛法、損失威光、誤累眾生，大惡知識不得佛意，其過如是。

Furthermore, when times are difficult and one is constrained by royal duties such that one cannot cultivate the wholesome, one is made to practice calming and contemplation in the midst of the unwholesome. You now face no difficulties and have no constraints; why do you intend to use only the milk medicine to poison the wisdom-life of others? Thus, in the Āgamas, the cowherd knows well the good fords, keeping the herd of cattle safe and secure. If the good ford presents difficulties and it is an unavoidable emergency, one must take the bad ford; but the bad ford has many perils, where not one in a hundred survives intact. You now have no troubles and fortunately are at the good ford, driving the cattle along the good path; why plunge yourself and others into ruin along the bad path? Destroying the Buddha-Dharma, diminishing its awe-inspiring brilliance, and misleading and entangling sentient beings—such are the faults of a great bad spiritual friend who does not grasp the Buddha's intent.