法苑珠林 30.40

30.40

如舍利弗問經云。舍利弗白佛言。云何如來告天帝釋及四天王云。我不久滅度。汝等各於方土護持我法。我去世後。摩訶迦葉賓頭盧君徒般歎羅睺羅四大比丘。住不泥洹流通我法。佛言。但像教之時信根微薄。雖發信心不能堅固。不能感致諸佛弟子雖專到累年。不如佛在世時一念之善故。彌勒下生聽汝泥洹。

As stated in the Śāriputraparipṛcchā-sūtra: Śāriputra said to the Buddha, "Why did the Tathāgata inform Śakra, Devendra, and the Four Heavenly Kings, saying: 'Before long I shall enter parinirvāṇa. You shall each protect and maintain my Dharma in your respective regions. After I pass away, the four great monks—Mahākāśyapa, Piṇḍola, Kuntadhāna, and Rāhula—shall abide without entering nirvāṇa to circulate my Dharma'?" The Buddha said, "It is merely that during the semblance teaching the root of faith is slight and frail; although they generate faith, they cannot be steadfast. Although [they may try] to evoke the Buddhas' disciples through single-minded devotion for consecutive years, it is not equal to a single moment of wholesome thought while the Buddha was in the world. Therefore, when Maitreya descends to be born, I permit you to enter nirvāṇa."