佛頂尊勝陀羅尼經教跡義記 2.72

2.72

唐云誓願加持也。解曰：誓願加持者，勸發進修普願成佛，轉凡成聖，故名誓願加持。又解：真言行者修瑜伽時，無散動時，密念誦時，寂靜證得時，布金剛壇上正諦觀時，如來誓願潛護加持也。

In Chinese it means: "Empowerment of vows." The explanation states: As for "empowerment of vows," it urges advancement in practice, universally vowing to attain Buddhahood and transforming from ordinary being into noble one; hence it is called "empowerment of vows." Another explanation: When the mantra practitioner cultivates yoga, when there is no distraction, when reciting esoterically, when quiescently realizing, when correctly and attentively contemplating on the arranged vajra altar, the Tathāgatas' vows secretly protect and empower them.