Ch 18, Sh 36-41, Bhagawad Gita, Shankar Bhashya

Idanim, now; srnu, hear; me, from Me i.e. be attentive to what I say; tu, as regards; the trividham, three kinds of; sukham, joy, O son of the Bharata dynasty. Yatra, that in which; ramate, one delights, derives pleasure; abhyasat, owing to habit, due to frequent repetition; and in the experience of which joy one nigacchati, certainly attains; duhkhantam, the cessation of sorrow.
Yat, that joy which is; iva, like; visam, poison, a source of pain; agre, in the beginning, when it first comes in the early stages of (acquisition) of knowledge, detachment, meditation and absorption, since they involve great struggle; but amrtopamam, comparable to nectar; pariname, in the end, when it arises from the maturity of knowledge, detachment, etc.; and which atma-buddhi-prasadajam, arises from the purity (prasada), transparence like water, of one's intellect (atma-buddhi); tat, that; sukham, joy; is proktam, spoken of, by the learned ones ;as sattvikam, born of sattva. Or, the phrase atma-buddhi-prasadajam may mean 'arising from the high degree of clearness of that atma-buddhi (knowledge of or connected with the Self); therefore it is born of sattva.
Tat, that; sukham, joy; is smrtam, referred to; as rajasam, born of rajas; yat, which; visaya-indriya-samyogat, arising from the contact of the organs and (their) objects; is amrtopamam, like nectar; agre, in the beginning, in the initial moments; but iva, like; visam, poison; pariname, at the end-at the end of full enjoyment of the objects (of the senses), because it causes loss of strength, vigor, beauty, wisdom, [Prajna, the capacity to understand whatever is heard.] retentive faculty, wealth and diligence, and because it is the cause of vice and its consequent hell etc.
That joy is udahrtam, said to be; tamasam, born of tamas; yat, which; both agre, in the beginning; ca, and; anubandhe, in the sequel, after the end (of enjoyment); is mohanam, delusive; atmanah, to oneself; and nidra-alasya-pramada-uttham, arises from sleep, laziness and inadvertence.
Therefore, now is begun a verse in order to conclude this section.
Na asti, there is no; tat, such; sattvam, entity, living creatures like men and others, or non-living things; prthivyam, in the world; va punah, or, again; an entity devesu, among the gods; divi, in heaven; yat, which; syat, can be [this is connected with the preceding portion 'na tat, there is no such (entity)']; muktam, free; hih, from these; trubhih, three; gunaih, gunas, sattva etc.; prakrti-jaih, born of Nature.
Parantapa, O scorcher of enemies; karmani, the duties; brahmana-ksatriya-visam, of the Brahmanas, the Ksatriyas and the Vaisyas; ca, as also; sudranam, of the Surdras-the Sudras; pravibhaktani, have been fully classified, according to what?-gunahi, according to the gunas; svabhava-prabhavaih, born from Nature.