New version available here: vedabase.io

SB 5.19.19

asminn eva varṣe puruṣair labdha-janmabhiḥ śukla-lohita-kṛṣṇa-varṇena svārabdhena karmaṇā divya-mānuṣa-nāraka-gatayo bahvya ātmana ānupūrvyeṇa sarvā hy eva sarveṣāṁ vidhīyante yathā-varṇa-vidhānam apavargaś cāpi bhavati.
Synonyms: 
asmin eva varṣe — in this tract of land (Bhārata-varṣa); puruṣaiḥ — by the people; labdha-janmabhiḥ — who have taken birth; śukla — of the mode of goodness; lohita — of the mode of passion; kṛṣṇa — of the mode of ignorance; varṇena — according to the division; sva — by himself; ārabdhena — begun; karmaṇā — by activities; divya — divine; mānuṣa — human; nāraka — hellish; gatayaḥ — goals; bahvyaḥ — many; ātmanaḥ — of his own; ānupūrvyeṇa — according to acts performed previously; sarvāḥ — all; hi — certainly; eva — indeed; sarveṣām — of all of them; vidhīyante — are allotted; yathā-varṇa-vidhānam — in terms of different castes; apavargaḥ — the path of liberation; ca — and; api — also; bhavati — is possible.
Translation: 
The people who take birth in this tract of land are divided according to the qualities of material nature — the modes of goodness [sattva-guṇa], passion [rajo-guṇa], and ignorance [tamo-guṇa]. Some of them are born as exalted personalities, some are ordinary human beings, and some are extremely abominable, for in Bhārata-varṣa one takes birth exactly according to one’s past karma. If one’s position is ascertained by a bona fide spiritual master and one is properly trained to engage in the service of Lord Viṣṇu according to the four social divisions [brāhmaṇa, kṣatriya, vaiśya and śūdra] and the four spiritual divisions [brahmacārī, gṛhastha, vānaprastha and sannyāsa], one’s life becomes perfect.
Purport: 

For further information, one should refer to Bhagavad-gītā (14.18 and 18.42-45). Śrīla Rāmānujācārya writes in his book Vedārta-saṅgraha:

evaṁ-vidha-parābhakti-svarūpa-jñāna-viśeṣasyotpādakaḥ pūrvoktāharahar upacīyamāna-jñāna-pūrvaka-karmānugṛhīta-bhakti-yoga eva; yathoktaṁ bhagavatā parāśareṇa — varṇāśrameti. nikhila-jagad-uddhāraṇāyāvanitale ’vatīrṇaṁ para-brahma-bhūtaḥ puruṣottamaḥ svayam etad uktavān — “svakarma-nirataḥ siddhiṁ yathā vindati tac chṛṇu” “yataḥ pravṛttir bhūtānāṁ yena sarvam idaṁ tatam/ svakarmaṇā tam abhyarcya siddhiṁ vindati mānavaḥ.”

In the Viṣṇu Purāṇa (3.8.9), the great sage Parāśara Muni has recommended:

varṇāśramācāravatā
 puruṣeṇa paraḥ pumān
viṣṇur ārādhyate panthā
 nānyat tat-toṣa-kāraṇam

“The Supreme Personality of Godhead, Lord Viṣṇu, is worshiped by the proper execution of prescribed duties in the system of varṇa and āśrama. There is no other way to satisfy the Lord.” In the land of Bhārata-varṣa, the institution of varṇāśrama-dharma may be easily adopted. At the present moment, certain demoniac sections of the population of Bhārata-varṣa are disregarding the system of varṇāśrama-dharma. Because there is no institution to teach people how to become brāhmaṇas, kṣatriyas, vaiśyas and śūdras or brahmacārīs, gṛhasthas, vānaprasthas and sannyāsīs, these demons want a classless society. This is resulting in chaotic conditions. In the name of secular government, unqualified people are taking the supreme governmental posts. No one is being trained to act according to the principles of varṇāśrama-dharma, and thus people are becoming increasingly degraded and are heading in the direction of animal life. The real aim of life is liberation, but unfortunately the opportunity for liberation is being denied to people in general, and therefore their human lives are being spoiled. The Kṛṣṇa consciousness movement, however, is being propagated all over the world to reestablish the varṇāśrama-dharma system and thus save human society from gliding down to hellish life.