Bhagavad Gita · Dhyana Yoga (Atma-samyama Yoga)Chapter 6, Shloka 1 (6.1)

"Niragni" and "akriya". The Vedic renunciate gave up the sacrificial fire (agni) — hence niragni; and all rites — hence akriya. Krishna says: no one becomes a renunciate or a yogi merely through outward giving up.

Shankaracharya — in a "gauṇa" (secondary) sense. Anāśritaḥ karma-phalaṃ … karma-phala-tṛṣṇā-rahita ity arthaḥ — free of craving for the fruit. Such a person performs kāryaṃ … nityaṃ kāmya-viparītam agnihotrādikaṃ karma — the obligatory, desireless actions (agnihotra and the like). Then Shankara himself raises an objection: in shruti and smriti it is precisely the niragni, akriya who is called a renunciate! Answer: kayācit guṇa-vṛttyā — both names are given by some resemblance of quality: karma-phala-saṃkalpa-saṃnyāsāt saṃnyāsitvam — "renunciate" because the intention for the fruit is renounced; citta-vikṣepa-hetoḥ parityāgāt yogitvam — "yogi" because the intention that distracts the mind is given up; gauṇam ubhayam na punaḥ mukhyam — both names are secondary, not primary. That is, it is praise of the karma yogi, but the primary renunciation is the wise one's giving up of all action.

Acharya Ramanuja — truly both forms of steadfastness. Kāryaṃ karmānuṣṭhānam eva … asmat-suhṛd-bhūta-parama-puruṣārādhana-rūpatayā — performing action is itself the duty, because it is worship of the Supreme Person who is our friend (a direct link with 5.29); karmaiva mama prayojanaṃ na tat-sādhyaṃ kiñcit — "action itself is my purpose, not anything gained by it." Such a person is sannyāsī ca jñāna-yoga-niṣṭhaś ca yogī ca karma-yoga-niṣṭhaś ca — established in both jnana yoga and karma yoga. And na niragnir na cākriyaḥ … kevala-jñāna-niṣṭhaḥ tasya hi jñāna-niṣṭhā eva — one who is only steadfast in knowledge has just one form of steadfastness; the karma yogi has ubhayam — both.

The difference: Shankara — calling the karma yogi a "renunciate" is praise (secondary); Ramanuja — the karma yogi truly holds both knowledge and action.