大毘盧遮那成佛神變加持經蓮華胎藏菩提幢標幟普通真言藏廣大成就瑜伽 3.162

3.162

「所疑不淨者，皆觀囕字燒，
辦事加持身，十力明方食。」

"Regarding that which is suspected to be impure, visualize the syllable RAṂ burning it;
Empower the body with the accomplishment of actions, and only after reciting the vidyā of the Ten Powers should one eat."