The characters of 'Heizei Gojo' appear in "Shoshinge Taii" ("Summary of the Shoshinge Sutra") and "Ofumi" ("letters") both written by Rennyo (a priest of the Jodo Shinshu school).
「平生業成」の文字そのものは、蓮如の『正信偈大意』『御文』に出てくる。