Why Bhagavad Gita is called as a Yoga Shastra or Sacred scripture of Yoga

Bhagavad Gita is called a yoga-shastra, because yoga is taught in it. In Fact, the name of all eighteen Chapters ends with word Yoga. But, the word Yoga, I am not implying the most common misnomer or exercises for the body. The word Yoga is perhaps the most widely misunderstood term and most of the times people consider that doing some postures, controlled breathing and the body and generally practiced for the physical health. I also heard many other terms like, Hot Yoga and even Hip hop Yoga. So going with what most people generally think Yoga is - Physical exercise and breathing is actually a part of Astanga Yoga, which involves controlling the mind and following the Asta angas or eight limbs like, Yama, Niyama,Asana, Pranayama,Pratyahara, Dharana,Dhyana, Samadhi.Then, apart from Astanga Yoga, there are other yogas explained in Gita, which are like Karma Yoga - Yoga of work and renunciation, Jnana Yoga - Yoga of knowledge, Bhakti Yoga - Yoga of devotional service. 

The word “yoga” is used 78 times in the Bhagavad Gita, Including variants like “yogi” (found 28 times) and yukta(found 49 times),it appears 155 times. The word yukta which means connected. Yogi is one who practices yoga, Yukta is one who is connected(with the Supreme God).

The total number of Chapters in Bhagavad Gita is 18 and the number of verses is 700. Thus, 20% of Gita's verses have the word yoga or its related forms. Apart from direct mention of the word Yoga, Lord Krishna talks about Yoga, what is a Yoga, who is a yogi etc in number of verses. Just to give you a feel, I have given below a list of few verses from initial chapters of Bhagavad Gita.

Bg 2.48 — Perform your duty equipoised, O Arjuna, abandoning all attachment to success or failure. Such equanimity is called yoga.

Bg 2.50 — A man engaged in devotional service rids himself of both good and bad reactions even in this life. Therefore strive for yoga, which is the art of all work.

Bg 4.28 — Having accepted strict vows, some become enlightened by sacrificing their possessions, and others by performing severe austerities, by practicing the yoga of eightfold mysticism, or by studying the Vedas to advance in transcendental knowledge.

Bg 4.42 — Therefore the doubts which have arisen in your heart out of ignorance should be slashed by the weapon of knowledge. Armed with yoga, O Bhārata, stand and fight.

Bg 5.4 — Only the ignorant speak of devotional service [karma-yoga] as being different from the analytical study of the material world [Sankhya]. Those who are actually learned say that he who applies himself well to one of these paths achieves the results of both.

Bg 6.2 — What is called renunciation you should know to be the same as yoga, or linking oneself with the Supreme, O son of Pandu, for one can never become a Yogi unless he renounces the desire for sense gratification.

Bg 6.3 — For one who is a neophyte in the eightfold yoga system, work is said to be the means; and for one who is already elevated in yoga, cessation of all material activities is said to be the means.

Bg 6.4 — A person is said to be elevated in yoga when, having renounced all material desires, he neither acts for sense gratification nor engages in fruitive activities.

Bg 6.11-12 — To practice yoga, one should go to a secluded place and should lay kuśa grass on the ground and then cover it with a deerskin and a soft cloth. The seat should be neither too high nor too low and should be situated in a sacred place. The yogī should then sit on it very firmly and practice yoga to purify the heart by controlling his mind, senses and activities and fixing the mind on one point.

Bg 6.17 — He who is regulated in his habits of eating, sleeping, recreation and work can mitigate all material pains by practicing the yoga system.

Bg 6.18 — when the yogi, by practice of yoga, disciplines his mental activities and becomes situated in transcendence – devoid of all material desires – he is said to be well established in yoga.

Bg 6.20-23 — In the stage of perfection called trance, or samadhi, one’s mind is completely restrained from material mental activities by practice of yoga. This perfection is characterized by one’s ability to see the Self by the pure mind and to relish and rejoice in the Self. In that joyous state, one is situated in boundless transcendental happiness, realized through transcendental senses. Established thus, one never departs from the truth, and upon gaining this he thinks there is no greater gain. Being situated in such a position, one is never shaken, even in the midst of greatest difficulty. This indeed is actual freedom from all miseries arising from material contact.

Bg 6.24 — One should engage oneself in the practice of yoga with determination and faith and not be deviated from the path. One should abandon, without exception, all material desires born of mental speculation and thus control all the senses on all sides by the mind.

Bg 6.28 — Thus the self-controlled yogi, constantly engaged in yoga practice, becomes free from all material contamination and achieves the highest stage of perfect happiness in transcendental loving service to the Lord.

Bg 6.33 — Arjuna said: O Madhusūdana, the system of yoga which You have summarized appears impractical and unendurable to me, for the mind is restless and unsteady.

Bg 6.42 — Or [if unsuccessful after long practice of yoga] he takes his birth in a family of transcendentalists who are surely great in wisdom. Certainly, such a birth is rare in this world.

Bg 6.47 — And of all yogi, the one with great faith who always abides in Me, thinks of Me within himself and renders transcendental loving service to Me – he is the most intimately united with Me in yoga and is the highest of all. That is My opinion.

(Translation of the Verses by His Divine Grace Srila Prabhupad – Bhagavad Gita As it is.

Thus by the sheer number of times, the word Yoga being repeated and the essence of the teachings of Gita, we can understand that Bhagavad Gita is a Yoga Shastra or a scripture that endows one with knowledge of Yoga.