BhG 6.6

syntax

yena eva (by whom only) ātmanā eva (by the self) ātmā (self) jitaḥ (conquered) [asti] (is),
tasya (of his) ātmā (self) ātmanaḥ (of the self) bandhuḥ (a friend) [asti] (is).
anātmanaḥ tu (but of one who has no self) ātmā (self) śaru-vat eva (like an enemy only) śatrutve (in enmity) varteta (it would act).

grammar

bandhuḥ	–	bandhu 1n.1 m. – relative, friend (√bandh – to bind, to fetter);
ātmā	–	ātman 1n.1 m. – self;
ātmanaḥ	–	ātman 6n.1 m. – of the self;
tasya	–	tat sn. 6n.1 m. – his;
yena	–	yat sn. 3n.1 m. – by whom;
ātmā	–	ātman 1n.1 m. – self;
eva	–	av. – certainly, just, merely;
ātmanā	–	ātman 3n.1 m. – by the self;
jitaḥ	–	jita (√ji – to conquer) PP 1n.1 m. – conquered, defeated;
anātmanaḥ	–	an-ātman 6n.1 m.; BV: yasyātmā [jito] nāsti saḥ – of one who did not [conquered] the  self; of one to whom the self does not belong (from: ātman – self);
tu	–	av. – but, then, or, and;
śatrutve	–	śatru-tva abs. 7n.1 n. – in enmity (from: √śad – to fall, to disperse, to kill; śatru – enemy, rival);
varteta	–	√vṛt (to move, to happen, to act) Pot. Ā 1v.1 – it would act;
ātmā	–	ātman 1n.1 m. – self;
eva	–	av. – certainly, just, merely;
śatru-vat	–	av. – like an enemy (from: √śad – to fall, to disperse, to kill; śatru – enemy, rival; -vat – suffix: as, like);

textual variants

yenātmaivātmanā jitaḥ → paramātmaivātmanā jitaḥ (with the self the supreme self only conquered);
anātmanas tu → ajitātmanas tu (but of one who did not conquere the self);
śatru-vat → śatru-jit (who conquered the enemies);

Śāṃkara

ātmaiva bandhur ātmaiva ripur ātmana ity uktam | tatra kiṃ-lakṣaṇa ātmā ātmano bandhuḥ, kiṃ-lakṣaṇo vā ātmātmano ripur ity ucyate—

bandhur ātmātmanas tasya, tasyātmanaḥ sa ātmā bandhur yenātmanātmaiva jitaḥ | ātmā kārya-karaṇa-saṃghāto yena vaśīkṛtaḥ, jitendriya ity arthaḥ | anātmanas tv ajitātmanas tu śatrutve śatru-bhāve varteta ātmaiva śatruvat, yathānātmā śatrur ātmano’pakārī, tathātmā ātmano’pakāre varteta ity arthaḥ

Rāmānuja

yena puruṣeṇa svenaiva svamano viṣayebhyo jitam, tanmanas tasya bandhuḥ / anātmanaḥ ajitamanasaḥ svakīyam eva manaḥ svasya śatruvac śatrutve varteta svaniśśreyasaviparīte vartetetyarthaḥ / yathoktaṃ bhagavatā parāśareṇāpi, „mana eva manuṣyāṇāṃ kāraṇaṃ bandhamokṣayoḥ / bandhāya viṣayāsaṅgi muktyaiva nirviṣayaṃ manaḥ

Śrīdhara

katham-bhūtasyātmaiva bandhuḥ ? katham-bhūtasya cātmaiva ripur ity apekṣāyām āha bandhur iti | yenātmanaivātmā kārya-kāraṇa-saṅghāta-rūpo jito vaśīkṛtasya tathābhūtasyātmana ātmaiva bandhuḥ | anātmano ‚jitātmanas tv ātmaivātmanaḥ śatrutve śatruvad apakāra-kāritve varteta

Madhusūdana

idānīṃ kiṃ-lakṣaṇa ātmātmano bandhuḥ kiṃ-lakṣaṇo vātmano ripur ity ucyate bandhur iti | ātmā kārya-karaṇa-saṃghāto yena jitaḥ sva-vaśīkṛta ātmanaiva viveka-yuktena manasaiva na tu śastrādinā | tasyātmā svarūpam ātmano bandhur ucchṛṅkhala-sva-pravṛtty-abhāvena sva-hita-karaṇāt | anātmanas tv ajitātmana ity etat | śatrutve śatru-bhāve vartetātmaiva śatruvat | bāhya-śatrur ivocchṛṅkhala-pravṛttyā svasya svenāniṣṭācaraṇāt

Viśvanātha

kasya sa bandhuḥ ? kasya sa ripur ity apekṣāyām āha bandhur iti | yenātmanā jīvenātmā mano jitas tasya jīvasya sa ātmā mano bandhuḥ | anātmano ‚jita-manasas tv ātmaiva mana eva śatruvat śatrutve ‚pakārakatve varteta

Baladeva

kīdṛśasya sa bandhuḥ ? kīdṛśasya sa ripur ity apekṣāyām āha bandhur iti | yenātmanā jīvenātmā mana eva jitas tasya jīvasya sa ātmā mano bandhus tad-upakārī | anātmano ‚jita-manasas tu jīvasyātmaiva mana eva śatruvat śatrutve ‚pakārakatve varteta