स्वाध्यायज्ञानयज्ञाश्च यतयः संशितव्रताः।।4.28।।
4.28. [These] are [respectively] the performs of sacrifices with material objects, the performers of sacrifices with penance, and the performers of sacrifices with Yoga. Likewise [there are] yet other ascetics with rigid vows whose sacrifices are the svadhyaya-knowledge.
4.27-28 Sarvani etc. Dravyayajnak etc. Again all the activities of their sense-organs, the activities of their mind, and the activities of their vital airs, such as issuing through the mouth and nose, driving down the urine etc., other [seekers] established in the fire of concentration, named Yoga, which is the means for subduing the self i.e., the mind, and which is set ablaze by i.e., to be filled with, knowledge. The idea is this : With their intellect that has completely abandoned all other activities due to their concentration on the object, they receive the object that is being perceived on conceived. That has been stated in the Sivopanisad : When the intellect, concentrated on a certain object, not rejected, would not go to another object, at that time the meditation, remaining in the core of the objects, blossoms very much. Thus the Yoga-sacrifices are explained. So far the performers of the material-object-sacrifices, the austerity-sacrifices, and the yoga-sacrifices have been defined. Those, who are the performers of the svadhyaya-knowledge-sacrifices are defined now [as] -
Dravyayajnaas tapoyajnaa yogayajnaastathaapare; Swaadhyaayajnaana yajnaashcha yatayah samshitavrataah.
dravya-yajñāḥ—offering one’s own wealth as sacrifice; tapaḥ-yajñāḥ—offering severe austerities as sacrifice; yoga-yajñāḥ—performance of eight-fold path of yogic practices as sacrifice; tathā—thus; apare—others; swādhyāya—cultivating knowledge by studying the scriptures; jñāna-yajñāḥ—those offer cultivation of transcendental knowledge as sacrifice; cha—also; yatayaḥ—these ascetics; sanśhita-vratāḥ—observing strict vows