B.G 4.28

द्रव्ययज्ञास्तपोयज्ञा योगयज्ञास्तथापरे। स्वाध्यायज्ञानयज्ञाश्च यतयः संशितव्रताः ॥२८॥

dravyayajñāstapoyajñā yogayajñāstathāpare। svādhyāyajñānayajñāśca yatayaḥ saṁśitavratāḥ ॥28॥

[द्रव्य यज्ञाः तपो यज्ञा योग यज्ञाः तथा अपरे। स्वाध्याय ज्ञान यज्ञाः च यतयः संशित व्रताः॥
dravya yajñāḥ = sacrifice of wealth; tapo yajñā = sacrifice in the form of practice; yoga yajñāḥ = sacrifice in the form of Yōga; tathā apare = similarly others;। svādhyāya jñāna yajñāḥ = sacrifice in the form of self study and knowledge; ca = and; yatayaḥ = practitioners; saṁśita vratāḥ = are the resolute observances;]

Sacrifice in the form of self-study and knowledge, sacrifice in the form of Yōga, sacrifice in the form of practice, sacrifice in the form of offering wealth, and others are respectively the resolute observances.

Gīta Bhāshya 4.28

'dravyayajñāḥ' - offering of wealth. 'tapoyajñā' - practicing the attitude of offering to the supreme lord. The act of offering to the supreme lord alone is indeed the understanding of sacrifice, symbolized by oblation into fire.

द्रव्यं जुह्वतीति द्रव्ययज्ञाः। तपः परमेश्वरार्पण बुद्ध्या तत्र जुह्वतीति तपोयज्ञा इत्यादि। इदं तपः हविः। तत् ब्रह्माग्नौ जुहोमि तत्पूजार्थम् इति होमः। तदर्पणे एव च होमबुदि्धः ॥२८॥

dravyaṁ juhvatīti dravyayajñāḥ। tapaḥ parameśvarārpaṇa buddhyā tatra juhvatīti tapoyajñā ityādi। idaṁ tapaḥ haviḥ। tat brahmāgnau juhomi tatpūjārtham iti homaḥ। tadarpaṇe eva ca homabudidhaḥ ॥28॥

[dravyaṁ = the weakth; juhvatīti = is offered, therefore; dravyayajñāḥ = sacrifice of wealth; tapaḥ = 'tapa' i.e. practice is; parameśvarārpaṇa buddhyā = is the attitude of offering to the supreme lord; tatra = here; juhvatīti = offers; tapoyajñā = is 'tapoyajñā', i.e. sacrifice of practice; ityādi = and so on; idaṁ = this kind of; tapaḥ = practice; haviḥ = is the oblation; tat = that; brahmāgnau = in the fire of Brahman; juhomi = I offer; tatpūjārtham = for the purpose of worshiping that; iti = thus; homaḥ = offering into the fire; tadarpaṇe = the act of offering to Him; eva = alone; ca = even/indeed is; homabudidhaḥ = the mentality of offering into the fire;]

They offer wealth, hence it is called 'dravyayajñāḥ', i.e. sacrifice of wealth. The word 'tapoyajñā', i.e. sacrifice of practice, means practicing the attitude of offering to the supreme lord. In this context, such a practice itself is oblation. The offering into the fire is - "With the purpose of worshiping Him, I offer into the fire of Brahman". The act of offering Him alone is indeed the understanding of sacrifice, symbolized by oblation into fire.