Previously:  Krishna teaches Essence of the Supreme Being and ways to reach him.

Krishna predicates that the individual soul is part of the supreme soul, the God himself. He beautifully compares the world to the Banyan tree, which has roots above and branches below reaching the ground, where they root secondary trunks all around. The Vedas are the leaves; the objects of the fine senses are the shoots abounding; the roots below proliferate continuously in the human world of actions, which bind men. One cannot recognize the beginning or the end; neither its shape. Hence cut down this tree of worldly affairs bottom-wise and search for refuge from which there is no return. "In that refuge there is neither sun nor moon, but myself. You, the individual, are part of the supreme soul. Please note that the brilliance of the one sun shining over the whole world as also of the moon is mine. It spreads over all creatures within and without. I am fire digesting food. Also I make creatures breathe in and breathe out. Two things are existent mainly in this world, the indestructible and the destructible ones. Besides these, is the Purushottama, the highest one."

Non-violence, truthfulness, absence of anger, peace, kindness, firmness, modesty, kindness to animals, forgiveness, cleanliness, loyalty, amour-proper, are godly qualities; opposite words would describe the ungodly and the impious. The wicked people neither engage in good work, nor retire from evil ones. They are dirty, lying, and of bad conduct. Their work entails of decency. Being always self-centered they desire the destruction of their enemies. "They will be reborn as wicked in successive rebirths; they can never approach me. When freed from such vices, they will come unto me."

Arjuna asks, "A person ignores the rules of duct laid down in the shastras or holy books; but he worships with faith; do you define work as satvik (good) or Rajas (emotional) The reply is that the satva (good) worship is based on Shastras, as also on faith, without a desire for fame, fruit or credit. Shastras warrant religious authority. (The non-Brahmin Saints of India like Kanakadas, Soordas and Tukaram would challenge this statement; see Bhakti - the path of devotion) Thereafter, Krishna dilates upon the three types of food; the good would prefer satvik food (healthy, delicious and unctuous. The middle ones (Rajas) would prefer hot, sour, or salty and the last the ignorant would do with stale, the leftovers, or the tasteless fillings. Similarly the three types of festivities are performed with faith and rites for celebrity or evil to enemies. Krishna lays great stress on sacrifice which calls devotional act; as usual he has given a new meaning to sacrifice which was going out of use. He recommends daana (gifts given in charity) and tapas (penance). Faith is given primacy in all three acts sacrifice, charity and penance though reference to sacred books is advised.

To a question from Arjuna, Krishna replies that real sanyaasa (renunciation) is abandonment of selfish actions and tyaga (giving up) is abandonment of all fruits of action. As if looking askance at his own startling definition, limiting the scope of words, and the then popular word "actionlessness," the Lord brings Arjuna to the brass tasks of the workaday world. Action consists of five elements (don't boast of having acted!), place or purpose, the doer, different instruments, various actions, and fifthly, luck. Without the pride of functioning, even the destruction of these enemies does not amount to murder. He says that  action is not binding. One should look at all things, with one worldview, or weltanschauung. The Lord avers that caste depends on one's natural proclivities. He advises Brahmins to be learned, the warriors (Kshaartiyas) to be brave, Vaishyas to be good merchants taking care of cattle and farmlands and the Shudras (a.k.a. Shoodras) to be faithful servants. 

It is regrettable that  in course of time, the large majority of Hindus, who were tradesmen and farmers have been reduced in number, due to farmers being downgraded into Shudras. The Shudras formerly few in number are now the majority not performing the rites of the Aryans. The Shudras or servitors at the time of composing the Gita hailed from prisoners of war or judicial condemnation, drunkards, etc. and are advised to serve faithfully.)

"One should never give up one's religion however unpleasant." It is pertinent to mention that Gita is the compendium of all-important Upanishadic teachings with an important stress on work. Getting assured that Arjuna has imbibed his teaching, Shri Krishna advises him to spread his message to the world.