Bhagavad Gita · Sankhya YogaChapter 2, Shloka 28 (2.28)

Three stages. The story of every being: avyakta (before — we cannot see it), vyakta (in the middle — we know it), avyakta (after — again we cannot see it). We know only the middle part — and we weep when it goes.

Shankaracharya's quotation. He quotes a shloka: "adarśanād āpatitaḥ punaś cādarśanaṃ gataḥ / nāsau tava na tasya tvaṃ vṛthā kā paridevanā" — "he came from the unseen and went back into the unseen; he is not yours, nor are you his — why this futile lament?" (A well-known shloka found in the Mahabharata)

Ramanuja's reading. Human beings and other creatures — as substance — are first in an unperceived state, in the middle perceived in human form, and afterwards again in an unperceived state — they remain within their own nature; so there is no cause for lament in this. According to Ramanuja, up to this point Krishna has shown that there is no cause for grief even on the view that "the body itself is the self".

"Kā paridevanā" — why lament? Note — Krishna uses the word paridevanā (lamentation, weeping and wailing), which conveys excessive, continuous grief.