婆羅門之法以火為天之口，火燒供物則諸天得食之云。是護摩供之所由來。百論疏上之中曰：「再供養火為欲生福，外道謂火是天口，故就朝瞑二時再供養火。問外道何故謂火法天口耶？答俱舍論云：有天從火中出語言：諸天口中有光明謂言是火。故云天口。（中略）正燒蘇等千八種物，令香氣上達諸天，天得食之，令人獲福。將欲燒時，前遣人咒，然後燒。」章安之涅槃經會疏三十二曰：「火天者火是天口。若供養之，但燒魚肉，煙氣至天，天得此氣，故是天口。」
The mouth of Brahma, or the gods, a synonym for fire, as that element devours the offerings; to this the 護摩 homa, or fire altar cult is attributed, fire becoming the object of worship for good fortune. Fire is also said to speak for or tell the will of the gods.
一天口 指火。古代印度婆羅門之法以火為天之口，火燒供物，香氣上達而諸天得食。此係密教修護摩供之由來。百論疏卷上之中引俱舍論之說，謂有天從火中發出語言，又諸天口中有光明，謂言是火，故外道以火為天口。〔涅槃經會疏卷三十二〕p1732