jnana-yajnena capy anye
yajanto mam upasate
Others, who engage in sacrifice by the cultivation of knowledge, worship the Supreme Lord as the one without a second, as diverse in many, and in the universal form.
Commentary by Srila Prabhupada
This verse is the summary of the previous verses. The Lord tells Arjuna that those who are purely in Krishna consciousness and do not know anything other than Krishna are called mahatma; yet there are other persons who are not exactly in the position of mahatma but who worship Krishna also, in different ways. Some of them have already been described as the distressed, the financially destitute, the inquisitive, and those who are engaged in the cultivation of knowledge. But there are others who are still lower, and these are divided into three: (1) he who worships himself as one with the Supreme Lord, (2) he who concocts some form of the Supreme Lord and worships that, and (3) he who accepts the universal form, the vishvarupa of the Supreme Personality of Godhead, and worships that. Out of the above three, the lowest, those who worship themselves as the Supreme Lord, thinking themselves to be monists, are most predominant. Such people think themselves to be the Supreme Lord, and in this mentality they worship themselves. This is also a type of God worship, for they can understand that they are not the material body but are actually spiritual soul; at least, such a sense is prominent. Generally the impersonalists worship the Supreme Lord in this way. The second class includes the worshipers of the demigods, those who by imagination consider any form to be the form of the Supreme Lord. And the third class includes those who cannot conceive of anything beyond the manifestation of this material universe. They consider the universe to be the supreme organism or entity and worship that. The universe is also a form of the Lord.
Commentary by Sri Visvanatha Cakravarti Thakur
Thus in this chapter and the previous chapter the ananya bhakta, also called the mahatma (BG 8.15), is shown to be superior to the other devotees such as the one who approaches the Lord to rid himself of suffering. Now the Lord shows three other types of devotees who have not been mentioned previously, who are inferior to the previously mentioned ones: those who worship themselves, those who worship pratlka or secondary forms, and those who worship the visva rupa.
Madhusudana Sarasvati explains the verse as follows. These others are unable to practice the sadhana of the mahatma mentioned previously. They worship by the sacrifice of knowledge mentioned in the sruti in this way: tvam va aham asmi bhagavo devate aham vai tvam asi: I am he and you are I.(Varaha Upanisad 33) They worship solely by a process of knowledge in which they identify themselves with God. Thus it is called jfiana yajna. Ca means “only” and api indicates that they give up other practices. Thus the meaning is: some, not desiring any other form of sadhana, worship me through the sacrifice of knowledge, denying difference, simply by contemplating the non-difference of the worshipper and the object of worship (ekatvena). These are the best of the three types. Inferior to this are others who, thinking of difference (prthaktvena) between worshipper and object of worship, worship me through sacrifice of knowledge in different external forms representing the Lord, according to the sruti statements such as adityo brahmety adesah: the sun is brahman, this is the instruction (Chandogya Upanisad 3.19.1) Others who are inferior to that, and are unable to worship either in non-difference or difference, worship me as the soul of all (visvato mukham), visva rupa, by many methods bahudha, by doing many activities and worshiping many devatas.
According to the tantrika idea, one who does not identify with the deva cannot worship that deva: nadevo devam arcayet. Such worship in which one thinks, “I am Gopala” is called ahamgrahopasana. The worship of the vibhutis of the Lord, taking one and worshipping separately, is called pratikopasana. In such worship the person thinks, “The Supreme Lord Visnu is non different from the sun, he is not different from Indra, he is not different from Soma.” Worship of the totality of the vibhutis, thinking “Visnu is everything” is called visva rupa upasana. These are the three types of jnana yajna.
Or the meaning of ekatvena prthaktvena can mean that the two states “I am Gopala” (oneness) and “I am the servant of Gopala,” (difference) are simultaneously contemplated by one person, just like the river going to the ocean is different and non-different from the ocean. In this case there are only two types of jnana yajna.