摩訶止觀 7.166

7.166

發願者，誓也。如許人物，若不分券，物則不定；施眾生善，若不要心，或恐退悔，加之以誓。又無誓願，如牛無御不知所趣；願來持行，將至所在。亦名陀羅尼，持善遮惡；如坯得火，堪可盛物。二乘生盡故不須願；菩薩生生化物，須總願、別願。四弘是總願，法藏、《華嚴》所說一一善行、陀羅尼，皆有別願。

Making vows means taking an oath. It is like promising an item to someone: if the deed is not divided, the item is not fixed; when giving goodness to sentient beings, if one does not seal it with a firm intention, one might fear regression and remorse, so one reinforces it with a vow. Moreover, without vows, one is like an ox without a driver, not knowing where to head; vows come to sustain practice and carry it to its destination. It is also called a dhāraṇī, holding onto the good and warding off the evil; like unbaked clay meeting fire, it becomes capable of holding things. The two vehicles have exhausted rebirths, so they do not need vows; bodhisattvas take rebirth after rebirth to transform beings, so they need general vows and specific vows. The four universal vows are the general vows; the individual wholesome practices and dhāraṇīs spoken of by Dharmākara and the Avataṃsaka all have specific vows.