B.G 3.38, 39, and 40

धूमेनाव्रियते वह्निर्यथाऽदर्शो मलेन च। यथोल्बेनावृतो गर्भस्तथा तेनेदमावृतम् ॥३८॥

dhūmēnāvriyatē vahniryathā'darśō malēna ca। yathōlbēnāvr̥tō garbhastathā tēnēdamāvr̥tam ॥38॥

[धूमेन आव्रियते वह्निः यथा आदर्शो मलेन च। यथा उल्बेन आवृतो गर्भः तथा तेन इदम् आवृतम् ॥३८॥
dhūmēna = by smoke; āvriyatē = covered; vahniḥ = fire; yathā = just as; ādarśō = mirror; malēna = by dirt; ca = and;। yathā = just as; ulbēna = by the embryo; āvr̥tō = covered; garbhaḥ = womb; tathā = similarly; tēna = by that (desire); idam = this supreme being, the being, and the inner heart; āvr̥tam = is covered;॥]

Just as fire covered by smoke, mirror covered by dirt, and the womb covered by the embryo, is not seen, similarly, this (supreme being, the inner heart and the being) are covered by that (desire).

आवृतं ज्ञानमेतेन ज्ञानिनो नित्यवैरिणा। कामरूपेण कौन्तेय दुष्पूरेणानलेन च ॥३९॥

āvr̥taṁ jñānamētēna jñāninō nityavairiṇā। kāmarūpēṇa kauntēya duṣpūrēṇānalēna ca ॥39॥

[आवृतं ज्ञानम् एतेन ज्ञानिनो नित्यवैरिणा। कामरूपेण कौन्तेय दुष्पूरेण अनलेन च॥
āvr̥taṁ = covered; jñānam = knowledge; ētēna = by this; jñāninō = of the knower; nityavairiṇā = by the eternal enemy;। kāmarūpēṇa = in the form of desire; kauntēya = O son of Kunti (Arjuna); duṣpūrēṇa = difficult to satisfy; analēna= like fire, does not stay as is; ca = and;॥]

O son of Kunti, Arjuna, This knowledge of the knower is covered by the eternal enemy in the form of desire that is difficult to satisfy, and is like a fire that does not stay as is.

इंद्रियाणि मनो बुद्धिरस्याधिष्ठानमुच्यते। एतैर्विमोहयत्येष ज्ञानमावृत्य देहिनम् ॥४०॥

iṁdriyāṇi manō budidharasyādhiṣṭhānamucyatē। ētairvimōhayatyēṣa jñānamāvr̥tya dēhinam ॥40॥

[इंद्रियाणि मनो बुद्धिः अस्य अधिष्ठानम् उच्यते। एतैः विमोहयति एष ज्ञानम् आवृत्य देहिनम्॥
iṁdriyāṇi = the senses; manō = the mind; buddhiḥ = intellect; asya = its; adhiṣṭhānam = foundation; ucyatē = it is said;। ētaiḥ = by these; vimōhayati = bewilders; ēṣa = these; jñānam = knowledge; āvr̥tya = having enveloped; dēhinam = the embodied one;॥]

It is said that the senses, the mind, and the intellect are the places where it resides. By these desire envelops the knowledge of the embodied one.

Gīta Tātparya 3.38, 39 and 40

Desire is not only difficult to satisfy, it can never be satisfied. Hence, words 'duṣpūrēṇa' and 'anala' are used respectively.

"अखिलप्रेरको विष्णुः ब्रह्माध्याः तदवान्तराः। असुरा अशुभेष्वेव कामादेरभिमानिनः॥ तत्र कामः कालनेमिः सर्वं धूममलोल्बवत्। शुभमध्याधमजनं क्रमादावृत्य तिष्ठति॥ महाशनस्य तस्येदं नालं तेनानलोऽग्निवत्। भुञ्जान इंद्रियाविष्टो ज्ञानास्त्रेणैव दह्यते॥"

इति ब्रह्मतर्के।

"akhilaprērakō viṣṇuḥ brahmādhyāḥ tadavāntarāḥ। asurā aśubhēṣvēva kāmādērabhimāninaḥ॥ tatra kāmaḥ kālanēmiḥ sarvaṁ dhūmamalōlbavat। śubhamadhyādhamajanaṁ kramādāvr̥tya tiṣṭhati॥ mahāśanasya tasyēdaṁ nālaṁ tēnānalō'gnivat। bhuñjāna iṁdriyāviṣṭō jñānāstrēṇaiva dahyatē॥"

iti brahmatarkē।

["akhilaprērakō = inspirer of everything; viṣṇuḥ = lord Vishnu; brahmādhyāḥ = Brahma and others; tadavāntarāḥ = among them;। asurā = demons; aśubhēṣvēva = as inauspicious; kāmādērabhimāninaḥ = starting with desires, etc., preside over;॥ tatra = there; kāmaḥ = desire; kālanēmiḥ= indeed, ruler of time; sarvaṁ = everything; dhūmamalōlbavat = like fluttering smoke;। śubhamadhyādhamajanaṁ = people belonging to auspicious, middle, and lower; kramādāvr̥tya = having enveloped sequentially; tiṣṭhati = stands;॥ mahāśanasya = of the great devourer; tasyēdaṁ = his, this; nālaṁ = not sufficient; tēnānalō'gnivat = by that, like a fire;। bhuñjāna = consuming; iṁdriyāviṣṭō = engaged in sensory pleasures; jñānāstrēṇaiva = only by the weapon of knowledge; dahyatē = is burned;॥]

[iti brahmatarkē = states Brahma Tarka;]

"Lord Vishnu is the inspirer of everything. Within it's ambit are Brahma and others. The Demons preside over the inauspicious like desires, etc. The demon named 'Kalanemi', the time, rules over desires, like a drifting smoke, covering all types of people: the auspicious, the middle, and the lower. This great devourer (mahāśana) consumes, engaged in sensory pleasures, never feeling satisfied (anala), like a fire. He can be destroyed only by the weapon of knowledge."

- states Brahma Tarka

ज्ञानावरणरूपेण इदमावृणोतीति आवृतं ज्ञानमिति पुनराह। न केवलं दुष्पूरो नालमिति मन्यते चेत्यनलः।

jñānāvaraṇarūpēṇa idamāvr̥ṇōtīti āvr̥taṁ jñānamiti punarāha। na kēvalaṁ duṣpūrō nālamiti manyatē cētyanalaḥ।

[jñānāvaraṇarūpēṇa = in the form of the covering of knowledge; idamāvr̥ṇōtīti = this covers, thus; āvr̥taṁ = covered is; jñānamiti = knowledge, thus; punarāha = is again stated;। na = not; kēvalaṁ = only; duṣpūrō = imperfect; nālamiti = not satisfied, thus; manyatē = consider; cētyanalaḥ = similar like fire;।]

The way it (desire) covers knowledge, similarly it (desire) also covers (senses) is conveyed by using the words 'jñānamāvr̥tya' again (3.40). It is not a repeatition. Not only it is 'duṣpūrēṇa', i.e. it is difficult to satisfy, it is 'anala' i.e. it cannot be satisfied, hence it is compared to fire.

'अग्नेरप्यनलः कामो यन्नालमिति मन्यते'

इति च ॥३७-४०॥

'agnērapyanalaḥ kāmō yannālamiti manyatē'

iti ca ॥37-40॥

['agnērapyanalaḥ = the way fire is never satisfied; kāmō = desire; yannālamiti = can never be satisfied; manyatē = thus it is considered by the wise']

[iti ca = states anceint proverb;]

"The way fire is never satisfied, desire also can never be satisfied, thus wise believe."

- states ancient proverb.