"....Krsna-sakha, Arjuna, is related with Krsna eternally. Eternally as friend. How eternally? What is the proof? There is in the Bhagavad-gita. When Arjuna inquired... When Krsna said that "This system of yoga I explained to the sun-god millions of years ago,"imam vivasvate yogam proktavan aham avyayam, at that time, to clear the idea, Arjuna, for our sake, he inquired, "My dear Krsna, we are contemporaries. You are born the other day along with me. How can I believe that millions of years ago You spoke this philosophy to the sun-god? So what is the answer?" The answer is, "My dear Arjuna, both you and Me, we take so many incarnations, but you forget. But I do not forget. I do not forget." Therefore Arjuna is always with Krsna. It is not that in this age, this millennium, Arjuna is friend of Krsna. No. He is eternal friend. He has made friendship with Krsna. It is never to be broken. It is never to be broken. So if you want to relish the rasa, the mellow, the taste of friendship, make friendship with Krsna. Krsna is prepared to make you friend. Therefore He comes: "Please come. Become My friend." But we are denying. Make Krsna your friend."
Srila Prabhupada Lecture on Srimad-Bhagavatam, 10-23-74, Mayapur
"The transcendental relation of Arjuna with Krsna is of the dearmost friendship. In the Bhagavad-gita the Lord Himself has claimed Arjuna as His dearmost friend. Every living being is thus related with the Supreme Lord by some sort of affectionate relation, either as servant or as friend or as parent or as an object of conjugal love. Everyone thus can enjoy the company of the Lord in the spiritual realm if he at all desires and sincerely tries for it by the process of bhakti-yoga."
"The Supreme Living Being is perfect in all relations with His pure devotee. Sri Arjuna is one of the typical pure devotees of the Lord reciprocating in the fraternal relationship, and the Lord's dealings with Arjuna are displays of friendship of the highest perfect order. He was not only a well-wisher of Arjuna but actually a benefactor, and to make it still more perfect the Lord tied him into a family relationship by arranging Subhadra's marriage with him. And above all, the Lord agreed to become a chariot driver of Arjuna in order to protect His friend from warfare risks, and the Lord became actually happy when He established the Pandavas to rule over the world. Arjuna remembered all these one after another, and thus he became overwhelmed with such thoughts."
Srimad-Bhagavatam 1:15:4 Purport
"In the Bhagavad-gita we can see that Arjuna desired not to fight with his brothers and relations just to satisfy his own personal desires. But when he heard the message of the Lord, Srimad Bhagavad-gita, he changed his decision and served the Lord. And for his doing so, he became a famous devotee of the Lord, for it is declared in all the scriptures that Arjuna attained spiritual perfection by devotional service to the Lord in friendship. The fighting was there, the friendship was there, Arjuna was there, and Krsna was there, but Arjuna became a different person by devotional service."
Srimad-Bhagavatam 1:8:42 Purport
"There are different stages of devotional service and God realization. Strictly speaking, anyone who accepts the existence of God is situated in devotional service. To acknowledge that God is great is something, but not much. Lord Caitanya, preaching as an acarya, a great teacher, taught that we can enter into a relationship with God and actually become God's friend. In the Bhagavad-gita Krsna showed Arjuna His universal form because Arjuna was His "very dear friend." Upon seeing Krsna as the Lord of the universes, however, Arjuna actually asked Krsna to forgive the familiarity of his friendship. Lord Caitanya goes beyond this point. Through Lord Caitanya we can become friends with Krsna, and there is no limit to this friendship. We can become friends of Krsna not in awe or adoration but in complete freedom. We can even relate to God as His father. This is not only the philosophy of the Caitanya-caritamrta but of Srimad-Bhagavatam as well. There are no other scriptures in the world in which God is treated as the son of a devotee. Usually God is seen as the almighty father who supplies the demands of His sons. The great devotees, however, sometimes treat God as a son in their execution of devotional service. The son demands, and the father supplies, and in supplying Krsna the devotee becomes like a father. Instead of taking from God, we give to God. It was in this relationship that Krsna's mother, Yasoda, told the Lord, "Here, eat this or You'll die. Eat nicely." In this way Krsna, although the proprietor of everything, depends on the mercy of His devotee. This is a uniquely high level of friendship, in which the devotee actually believes himself to be the father of Krsna."
Caitanya-caritamrta, Adi lila Introduction
"In Bhagavad-gita when Krsna appeared in His universal form Arjuna prayed, "My dear Krsna, I thought of You as my cousin-brother, and so I have shown disrespect to You in so many ways, calling You 'Krsna' or 'friend.' But You are so great that I could not understand." So that was the position of the Pandavas; although Krsna is the Supreme Personality of Godhead, the greatest among all greats, He remained with those royal brothers, being attracted by their devotion, by their friendship and by their love. That is the proof of how great this process of devotional service is. It can attract even the Supreme Personality of Godhead. God is great, but devotional service is greater than God because it attracts Him. People who are not in devotional service can never understand what great value there is in rendering service to the Lord."
Nectar of Devotion, Chapter 1
"How the sons of Pandu, the Pandavas, enjoy Krsna's association is described as follows: "When Sri Krsna arrived in Indraprastha, the capital of the Kurus, Maharaja Yudhisthira immediately came out to smell the flavor of Krsna's head." It is the Vedic custom that a superior smells the heads of his subordinates when the subordinates offer respect to the superior by touching his feet. Similarly, Arjuna and Bhima embraced Krsna with great jubilation, and the two younger brothers, namely Nakula and Sahadeva, touched the lotus feet of Krsna with tears in their eyes and offered their respects. In this way all the five Pandava brothers enjoyed the fraternal friendship of Krsna in transcendental mellow. Of the five Pandavas, Arjuna is the most intimately connected with Krsna. He has a nice bow called Gandiva in his hand. His thighs are compared to the trunks of elephants, and his eyes are always reddish. When Krsna and Arjuna are together on a chariot, they become celestial beauties, pleasing to the eyes of everyone. It is said that once Arjuna was lying on his bed with his head upon Krsna's lap and was talking and joking with Krsna in great relaxation, enjoying Krsna's company with smiling and great satisfaction."
Nectar of Devotion, Chapter 41
"Arjuna was in a relationship with the Lord as friend. Of course there is a gulf of difference between this friendship and the friendship found in the material world. This is transcendental friendship which cannot be had by everyone. Of course everyone has a particular relationship with the Lord, and that relationship is evoked by the perfection of devotional service. But in the present status of our life, we have not only forgotten the Supreme Lord, but we have forgotten our eternal relationship with the Lord. Every living being, out of the many, many billions and trillions of living beings, has a particular relationship with the Lord eternally. That is called svarupa. By the process of devotional service, one can revive that svarupa, and that stage is called svarupa-siddhi--perfection of one's constitutional position. So Arjuna was a devotee, and he was in touch with the Supreme Lord in friendship.
How Arjuna accepted this Bhagavad-gita should be noted. His manner of acceptance is given in the Tenth Chapter (10.12-14):
...Arjuna said: You are the Supreme Brahman, the ultimate, the supreme abode and purifier, the Absolute Truth and the eternal Divine Person. You are the primal God, transcendental and original, and you are the unborn and all-pervading beauty. All the great sages like Narada, Asita, Devala, and Vyasa proclaim this of You, and now You Yourself are declaring it to me. O Krsna, I totally accept as truth all that You have told me. Neither the gods nor the demons, O Lord, know Thy personality."
After hearing Bhagavad-gita from the Supreme Personality of Godhead, Arjuna accepted Krsna as param brahma, the Supreme Brahman. Every living being is Brahman, but the supreme living being, or the Supreme Personality of Godhead, is the Supreme Brahman. Param dhama means that He is the supreme rest or abode of everything; pavitram means that He is pure, untainted by material contamination; purusam means that He is the supreme enjoyer; sasvatam, original; divyam, transcendental; adi-devam, the Supreme Personality of Godhead; ajam, the unborn; and vibhum, the greatest, the all-pervading.
Now one may think that because Krsna was the friend of Arjuna, Arjuna was telling Him all this by way of flattery, but Arjuna, just to drive out this kind of doubt from the minds of the readers of Bhagavad-gita, substantiates these praises in the next verse when he says that Krsna is accepted as the Supreme Personality of Godhead not only by himself but by authorities like the sage Narada, Asita, Devala, Vyasadeva and so on. These are great personalities who distribute the Vedic knowledge as it is accepted by all acaryas. Therefore Arjuna tells Krsna that he accepts whatever He says to be completely perfect. Sarvam etad rtam manye: "I accept everything You say to be true." Arjuna also says that the personality of the Lord is very difficult to understand and that He cannot be known even by the great demigods. This means that the Lord cannot even be known by personalities greater than human beings. So how can a human being understand Sri Krsna without becoming His devotee?
Therefore Bhagavad-gita should be taken up in a spirit of devotion. One should not think that he is equal to Krsna, nor should he think that Krsna is an ordinary personality or even a very great personality. Lord Sri Krsna is the Supreme Personality of Godhead, at least theoretically, according to the statements of Bhagavad-gita or the statements of Arjuna, the person who is trying to understand the Bhagavad-gita. We should therefore at least theoretically accept Sri Krsna as the Supreme Personality of Godhead, and with that submissive spirit we can understand the Bhagavad-gita. Unless one reads the Bhagavad-gita in a submissive spirit, it is very difficult to understand Bhagavad-gita because it is a great mystery.
Just what is the Bhagavad-gita? The purpose of Bhagavad-gita is to deliver mankind from the nescience of material existence. Every man is in difficulty in so many ways, as Arjuna also was in difficulty in having to fight the Battle of Kuruksetra. Arjuna surrendered unto Sri Krsna, and consequently this Bhagavad-gita was spoken."
Bhaktivedanta Book Trust. HDG A.C. Bhaktivedanta Swami Srila Prabhupada.