The Lotus Sūtra 4.14

4.14

「佛亦如是，為菩薩時，教化我等，令發一切智心。而尋廢忘，不知不覺。既得阿羅漢道，自謂滅度，資生艱難，得少為足。一切智願，猶在不失。今者世尊覺悟我等，作如是言：『諸比丘！汝等所得，非究竟滅。我久令汝等種佛善根，以方便故，示涅槃相，而汝謂為實得滅度。』

"The Buddha is also like this: when he was a Bodhisattva, he instructed us to give rise to the mind of all-knowledge. But we soon neglected and forgot it, unaware and uncomprehending. Having attained the arhat path, we considered ourselves to have attained nirvāṇa; finding livelihood difficult, we were content with little. Yet the aspiration for all-knowledge still remained without being lost. Now the Bhagavat has awakened us, speaking thus: 'Bhikṣus! What you have attained is not ultimate nirvāṇa. Long ago I caused you to plant the Buddha's roots of goodness, but through upāya I displayed the appearance of nirvāṇa, and you thought that you had actually attained nirvāṇa.'"