BhG 3.7

syntax

he arjuna (O Arjuna!),
yaḥ tu (but he who) manasā (by the mind) indriyāṇi (the senses) niyamya (after restraining)
asaktaḥ [san] (being unattached) karmendriyaiḥ (by the senses of activities) karma-yogam (yoga of activity) ārabhate (he begins),
saḥ (he) viśiṣyate (he is distinguished).

grammar

yaḥ	–	yat sn. 1n.1 m. – he who;
tu	–	av. – but, then, or, and;
indriyāṇi	–	indriya 2n.3 n. – the senses (from: √ind – to be powerful);
manasā	–	manas 3n.1 n. – by the mind (from: √man – to think);
niyamya	–	ni-√yam (to restrain) absol. – after restraining;
ārabhate	–	ā-√rabh (to reach, to undertake, to begin) Praes Ā 1v.1 – he begins;
arjuna	–	arjuna 8n.1 m. – white, clear, Arjuna;
karmendriyaiḥ	–	karma-indriya 3n.3 n.; TP: karmaṇām indriyair iti – by the senses of activities (from: √kṛ – to do, karman – activity and its result; √ind – to be powerful, indriya – the senses; vāk-pāṇi-pāda-pāyūpastha-saṁjñakāni – they are named: organ of speech, hand, foot, anus, genital);
karma-yogam	–	karma-yoga 2n.1 m.; TP: karmaṇo yogam iti – yoga of activity (from: √kṛ – to do, karman – activity and its result; √yuj – to yoke, to join, to engage, yoga – yoga, yoking, application, a means, one of the schools of Hindu philosophy);
asaktaḥ	–	a-sakta (√sañj – to attach, to stick, to embrace) PP 1n.1 m. – unattached;
saḥ	–	tat sn. 1n.1 m. – he;
viśiṣyate	–	vi-√śiṣ (to distinguish) Praes. pass. 1v.1 – he is distinguished, the best;

textual variants

niyamya → samyamya (after restraining);
‘rjuna → naraḥ (a person);

Śāṃkara

The key:
an excerpt from the commented verse
quotes from the scriptures
starting polemic

But whoso, restraining the senses by mind, O Arjuna, engages in Karma-Yoga, unattached, with organs of action, he is esteemed.		yas tv indriyāṇi manasā niyamyārabhate ’rjuna | karmendriyaiḥ karma-yogam asaktaḥ sa viśiṣyate ||3.7||
If the ignorant man, who is only qualified for action, performs action with the hand, with the organ of speech, &c., restraining the organs of knowledge by mind and unmindful of the result, he is more worthy than the other, who is a hypocrite.		yas tu punaḥ karmaṇy adhikṛto ’jñaḥ buddhīndriyāṇi manasā niyamya ārabhate arjuna karmendriyaiḥ vāk-pāṇy-ādibhiḥ |kim ārabhate ity āha – karma-yogam asaktaḥ san phalābhisandhi-varjitaḥ sa viśiṣyate itarasmāt mithyācārāt ||3.7||

Rāmānuja

ataḥ pūrvābhyastaviṣayasajātīye śāstrīye karmaṇi indriyāṇy ātmāvalokanapravṛttena manasā niyamya taiḥ svata eva karmapravaṇair indriyair asaṅgapūrvakaṃ yaḥ karmayogam ārabhate, so ‚saṃbhāvyamānapramādatvena jñānaniṣṭhād api puruṣād viśiṣyate

Śrīdhara

etad-viparītaḥ karma-kartā tu śreṣṭha ity āha yas tv indriyāṇīti | yas tv indriyāṇi manasā niyamya īśvara-parāṇi kṛtvā karmendriyaiḥ karma-rūpaṃ yogam upāyam ārabhate ‚nutiṣṭhati | asaktaḥ phalābhilāṣa-rahitaḥ san | sa viśiṣyate viśiṣṭo bhavati citta-śuddhyā jñānavān bhavatīty arthaḥ

Madhusūdana

autsukya-mātreṇa sarva-karmāṇy asaṃnyasya citta-śuddhaye niṣkāma-karmāṇy eva yathā-śāstraṃ kuryāt | tasmāt yas tv iti | tu-śabdo ‚śuddhāntaḥ-karaṇa-saṃnyāsi-vyatirekārthaḥ | indriyāṇi jñānendriyāei śrotrādīni manasā saha niyamya pāpa-hetu-śabdādi-viṣayāsakter nivartya manasā viveka-yuktena niyamyeti vā | karmendriyair vāk-pāṇy-ādibhiḥ karma-yogaṃ śuddhi-hetutayā vihitaṃ karmārabhate karoty asaktaḥ phalābhilāṣa-śūnyaḥ san yo vivekī sa itarasmān mithyācārād viśiṣyate | pariśrama-sāmye ‚pi phalātiśaya-bhāktvena śreṣṭho bhavati | he ‚rjunāścaryam idaṃ paśya yad ekaḥ karmendriyāṇi nigṛhṇan jñānendriyāṇi vyāpārayan puruṣārtha-śūnyo ‚paras tu jñānendriyāṇi nigṛhya karmendriyāṇi vyāpārayan parama-puruṣārtha-bhāg bhavatīti

Viśvanātha

etad-viparītaḥ śāstrīya-karma-kartā gṛhasthas tu śreṣṭha ity āha yas tv iti | karma-yogaṃ śāstra-vihitam | asakto ‚phalākāṅkṣī viśiṣyate | asambhāvita-prasāditvena jñāna-niṣṭhād api puruṣād viśiṣṭaḥ iti śrī-rāmānujācārya-caraṇāḥ

Baladeva

etad-vaiparītyena sva-vihita-karma-kartā gṛhastho ‚pi śreṣṭha ity āha yas tv iti | ātmānubhava-pravṛttena manasendriyāṇi śrotrādīni niyamyāsaktaḥ phalābhilāṣa-śūnyaḥ san yaḥ karmendriyaiḥ karma-rūpaṃ yogam upāyam ārabhate ‚nutiṣṭhati sa viśiṣyate | sambhāvyamāna-jñānatvāt pūrvataḥ śreṣṭho bhavatīty arthaḥ