B.G 4.25 and 26

daivamevāpare yajñaṁ yoginaḥ paryupāsate। brahmāgnāvapare yajñaṁ yajñenaivopajuhvati ॥25॥

śrotrādīnīṁdriyāṇyanye saṁyamāgniṣu juhvati। śabdādīn viṣayānanya iṁdriyāgniṣu juhvati ॥26॥

Some engage in 'yajna' to worship the lord, while Yogis meditate on the absolute reality, the lord Brahman, as 'yajna'. Others make offerings into the fire of 'yajna', and consider it as 'yajna'. Some offer the senses such as hearing into the fire of restraint, while others offer the sensual objects such as sound into the fire of the senses.

Gīta Bhāshya 4.25 and 26

The contemplation and worship of the supreme lord itself is 'yajna'. The word 'Yajna' denotes the supreme reality in the form of the lord Bhagavan.

yajñabhedān āha - daivam ityādinā। daivaṁ bhagavantam। sa eva teṣāṁ yajñaḥ। bhagavadupāsanam yajñam, iti kriyā viśeṣaṇam। nānyat teṣām asti yatīnāṁ keṣāñcit। yajñaṁ bhagavantam।

Different types of 'yajna' are explained by 'daiva' and such verses. The word 'daivaṁ' refers to 'Bhagavan', the supreme lord. He alone is their 'yajna'. The contemplation and worship of the supreme lord itself is 'yajna'. Such is the speciality of the activity involving contemplation and worship. For some aspiring ascetics, there is no other (path). The word 'Yajna', i.e. sacrifice, itself denotes the supreme reality in the form of the lord Bhagavan.

"yajñena yajñam", "yajño viṣṇurdevatā"

"From Yajna, the sacrifice, attain Yajna, the lord.", "The Yajna is the deity in the form of lord Vishnu."

ityādiśrutibhyaḥ।

- are the Vēdic testimonials.

yajñena prasiddhenaiva। yajñaṁ prati yajñena juhvatīti sarvatra samam "taṁ yajñam" ityādau। uktaṁ ca

By well established and renowned tradition, the word "yajñena" means "by means of sacrifice". The word 'yajñaṁ' is used always to refer to the person, in this case the lord, for whose sake sacrifice is being conducted. Example of "taṁ yajñam" from Purusha sukta (Rig 10.90) is given as an example. It is also said:

"viṣṇuṁ rudreṇa paśunā brahmā jyeṣṭhena sūnunā। ayajanmānase yajñe pitaraṁ prapitāmahaḥ॥"

"The great grandfather Brahma worshipped his father Lord Vishnu by offering his eldest son Rudra as sacrifice in his mind."

iti ॥25,26॥

- states testimonial.