The Long Āgama Sūtra 2.96

2.96

於後夏安居中，佛身疾生，舉體皆痛，佛自念言：「我今疾生，舉身痛甚，而諸弟子悉皆不在，若取涅槃，則非我宜，今當精勤自力以留壽命。」

After the summer retreat, the Buddha became sick, and his whole body ached. The Buddha thought to himself, “Now, I’ve become sick, and my whole body is in pain, but none of my disciples are present. It wouldn’t be appropriate for me to obtain nirvāṇa. I must make effort to extend my life with my own power for now.”