法苑珠林 27.26

27.26

於是遂不收毒自投火中。佛言。爾時黑蛇者。今舍利弗是。昔受如此死苦猶不收毒。況今更取所棄之藥。

Thereupon it did not take back the poison, but cast itself into the fire. The Buddha said, 'The black snake at that time was Śāriputra today. In the past, having suffered such agony of death, he still would not take back the poison; how much less would he now take up medicine he has abandoned?'