Srimad-Bhagavad-Gitā-Upaniṣad is a part of the great epic Mahābhārata. It contains eighteen chapters and seven hundred verses. Of the eighteen chapters, the first six chapters discuss selfless karma-yoga, the next six chapters discuss bhakti-yoga and the last six chapters discuss jñāna-yoga.
In this age of Kali, devotional service to the Supreme Lord by human beings has been covered by karma (fruitive activities) and jñāna (impersonal knowledge). As a result, despite being the most advanced creation of the creator, human beings are transmigrating through eight million different species of life like birds and animals. After receiving the human form of life, which is rare even for the gods and goddesses, they are acting like animals, far from the ultimate goal of life.
The ultimate goal of the human form of life is not to become intoxicated by bodily happiness like animals; but rather to go back to the spiritual abode Goloka Vrndavana. By being constantly immersed in chanting the Supreme Lord’s transcendental holy names the ‘Hare Krsna Mahā mantra’, one enjoys complete bliss. This process of devotional service is the only means to attain the shelter of the Supreme Lord and go on to realize one’s constitutional position in the eternal service of Śrī Rādhā-Govinda.
Lord Krsnacandra is the embodiment of complete transcendental bliss. How can we make Krsnacandra appear within our hearts and thus taste transcendental bliss?
As described in scripture
sakala-bhuvana-madhyenirdhanāste pidhanya
nivasatihrdiyesamśrī-harerbhaktirekä harirapinija-lokamsarvathātovihāya
praviśatihrditeşāṁ bhakti-sūtropanaddhah
(śrī madbhāgavatamāhātmyam 3.73)
“Glorious are those in whose hearts unalloyed devotional service to the Supreme Lord is manifest, even though they may be the most poverty stricken in the fourteen worlds. Lord Krsna, being bound by the rope of devotional service, leaves His own abode Vaikuntha and enters their hearts.”
Although human beings have variegated activities, they have one objective in life that is to be happy. Devotional service is the only means to achieve actual happiness. Being intoxicated karma and jñana, they have neglected the process of devotional service. Thus they are tussling with the Lord’s illusory energy known as māyā.
In this way they are uselessly wasting their precious and rarely attained human life, entangled in the cycle of repeated birth and death. What to speak of this, even when the compassionate Supreme Lord personally appears in this world to deliver them from their miserable condition of life, unfortunate human beings fail to realise Him due to being bewildered by karma and jnana. For this reason, the Supreme Lord has manifested before us in the form of Srimad Bhagavad-gitä-Upaniṣad.

According to Srimad Bhagavad-gitä, Lord Krsna played the role of Arjuna’s charioteer during the battle between the Kauravas and Pandavas at the religious battlefield of Kurukşetra. By this pastime, Lord Krsna. tried to impress upon the living entities that this material world is like a full-fledged battlefield. Who attains victory in this battle? Only one who is favored by the Supreme Lord attains victory and relishes complete happiness.
From the description in Bhagavad-gitä, it appears the Kauravas had a far greater number of soldiers. Thus one would expect them to defeat the Pandavas. However, they were ultimately defeated by the Pandavas who were devotees of the Lord. Therefore, it should be concluded that the devotees who have bound the Supreme Lord in their hearts. by the rope of unalloyed devotional service will ultimately achieve victory by the mercy of the Supreme Lord. Similarly, in this age of Kali, by chanting the holy names of the Supreme Lord, one will achieve victory even in the present disturbing environment.
While standing on that battlefield, Lord Krsna, through Arjuna, personally instructed all living entities how to get free from the battle of material existence:
sarva-dharman parityajya mam ekam saranam vraja
aham tvām sarva-papebhyo mokşayişyāmi ma sucah
“Give up all types of religion (karma, jñāna, and so on) and simply surrender unto Me. I will personally free you from all sinful reactions. Therefore, do not fear at all.”
In this way, for one who completely surrenders to the Supreme Lord Krsna without deviation, Krsna Himself takes full responsibility to maintain him and to protect him from the reactions of his previously committed sinful activities.
This surrender is like the gateway to the realm of devotional service. If one wants to enter a house, he has to do so through the door. Similarly, the instructions of Srimad Bhagavad-gita Upanisad are like the door to devotional life. By daily reciting this literature in the proper method, human beings will gradually make advancement on the path of devotional service. Eventually they will attain the ultimate goal of life – devotional service to the Supreme Lord.
Srimad Bhagavad-gītā Upaniṣad has also been compared to a cow, which is the essence or source of all the Upaniṣads.
sarvopaniṣado gāvo dogdhā gopāla-nandanah partho vatsah sudhir bhokta dugdham gitāmṛtam mahat
“Srimad Bhagavad-gītā, the essence of all Upanisads, is compared to a cow. The cowherd boy Lord Krsnacandra is the milkman of this cow, Arjuna is the calf and the wise and learned devotees are the drinkers of this milk of Bhagavad-gītā.”
If a calf does not nuzzle the udder of its mother, it is very difficult for the milkman to milk the cow. In the same way, Arjuna induced the milk of the Lord’s nectarean words, which are most beneficial to all living entities, by asking Him confidential questions. Thus, this milk of Bhagavad-gītā has become available to the knowledgeable, the qualified and the pure devotees.
Having already drunk this nectarean milk in the form of the Supreme Lord Krsnacandra’s words, our most respected spiritual masters and all the other previous and later vaisnava ācāryas have instructed us to similarly relish it.
Adapted from the Introduction (by HDG Srila Bhakti Bibudha Bodhayan Goswami Maharaja) to Bhagavad- gītā (published in Bengali) by HDG Srila Bhakti Promode Puri Goswami Thakur