首楞嚴義疏注經 9.401

9.401

The Great Sage's profound compassion exhorts him not to take extinction, and his earnest entrustment is precisely for the present time. If we compare the present text with the earlier vows—'If even one sentient being has not attained Buddhahood, I will never take nirvāṇa here'—then teacher and pupil accomplish one another, unified in compassionate salvation; how expediential indeed was the four disciples' entering extinction!