摩訶止觀 4.127

4.127

三、教授者，能說般若，示道、非道；內外方便，通塞妨障，皆能決了。善巧說法，示教利喜，轉破人心。於諸方便，自能決了，可得獨行；妨難未諳，不宜捨也。經言：「隨順善師學，得見恒沙佛。」是名「教授」。

Third, the teacher: one who can explain prajñā, show the path and what is not the path, and resolve all inner and outer skillful means, obstructions, and obstacles. Skillfully expounding the Dharma, they demonstrate, instruct, benefit, and gladden, transforming and breaking through people's minds. If one can resolve all skillful means by oneself, one may practice alone; if one is not yet conversant with obstacles and difficulties, one should not leave [the teacher]. A sūtra says: "Following and obeying a good master to learn, one comes to see buddhas as numerous as the sands of the Ganges." This is called the "teacher."