本文先對秘密佛教在東亞的歷史及純密與雜密之分做了回顧與檢視，接著再進入正題。密續中的護摩（homa，火供或燒供、燒施，藏文Sbyin-sreg，同時見之於印度教及佛教教法）源於吠陀一事，明載於佛教密教部。就其源頭，吠陀時代事火之法（agnihotra）本跟火之祭祀本身無直接關係，而是跟天上之火——太陽之周行不墜之祕密不可分離。事火之法等於是護持日出日落，使太陽不至於掉落之符咒。然其意義在吠陀時代之後有所變化，成為流佈於民間持火、燒供、祈福之事。佛陀對於婆羅門之祭祀持反對態度，而阿含經典火之象徵意義則正負兼之。一則感官世界如同熊熊烈火，易燃起貪瞋痴之原；然而也只有智慧之火可將無明之毒滅絕。不過佛教真言法門之火供，其世俗面向昭然若揭。如此一來，密續護摩不但要跟印度教思想作出區隔，也要超越火供的現世欲求諸如息災、增益和調伏等法。於是乃有出世護摩跟入世護摩之分，三昧真火等智慧之光之象徵成為佛教護摩的另層意義。就東亞歷史而言，密續在中晚唐之宗教勢力榮景，可由法門寺地宮之出土文物見出。由地宮之舍利供養所表現之密續內容，可看到護摩之重要性及秘密佛教對宮庭信仰之影響力量，而護摩可能在唐代為祕續佛寺每日必做的儀軌。慧琳將護摩類比為祭四郊五岳等國之大祭，亦可見出其重大政治意涵。 This paper explores the transformation of a ritual from ancient Vedic India to Buddhist China in the Tang Dynasty to see how the alteration of agnihotra as a ritual relates to the development of Buddhist thought and practice.In India, agnihotra is related to the sun rather than sacrifice to fire in origin, as it is the maintenance of fire for the rising sun. Thus, it is appropriate to say that fire is inside the sun as heat and light is emitted from the sun. As a kind of sun-charm, agnihotra is meant to help maintain not only the routine rising of the sun, but also its daily course-from east to west during the day and from west to east during the night. The meaning of agnihotra was transformed to mean the sacrifice to Agni as well as sacred fire itself in due course of time. In Epic literature, the term is often connected with the maintenance of the sacred fire and offering oblation to it. Ultimately, agnihotra was identified with the general fire sacrifice, and became a means to attain the different worldly goals in human life.In Tantric Buddhism, agnihotra becomes homa and is further divided into worldly and otherworldly in the Mahāvairocanasūtra. As Buddhist Tantra is inseparable from Mahāyānist world of thought, the decipherment of the Tantra ultimately rests on Mahāyānist ideals of enlightenment. Thus, while worldly homa is concerned with worldly pursuit and empowerment, otherworldly homa becomes the light of wisdom of bodhicitta to consume avidyā. Homa must have been an important daily ritual in the Tantric temples in the later Tang Dynasty, as we still can witness in Japanese esoteric Buddhism nowadays. Huei-lin compares homa with imperial sacrifice which probably shows the importance of homa in the Tang in terms of its political overtones.
