三彌勒經疏 1.97

1.97

經曰「結跏趺坐」以下，第三命終形相。結者交也，跏者重也。釋迦盡緣故，右脇枕手入涅槃。彌勒染未盡故，二聖不同也。

From the text of the sūtra where it says, "Sitting cross-legged" onwards, this is the third [section], [explaining] the physical posture of his decease. "Crossing" means interlinking; "legged" means overlapping. Because Śākyamuni's conditions had come to an end, he entered nirvāṇa on his right side with his hand pillowing his head. Because Maitreya's defilements had not yet come to an end, the two sages differed.