妙法蓮華經文句 2.59

2.59

本迹者，妻則齊也，豈有博地為太子妻？故知本住寂定微妙法喜，迹為佛妻。《悲花》云：「寶藏佛所，誓願為妻耳。」

As for origin and traces: 'wife' means equal; how could someone bound to the earth be the wife of the crown prince? Therefore we know that originally she abode in the subtle, wondrous Dharma joy of quiescent concentration; as traces, she was the Buddha's wife. The Karuṇāpuṇḍarīka-sūtra states: "Before the Buddha Ratnagarbha, she made a vow to become his wife."