Of all religio-philosophical portions of the Mahabharata the Bhagavad Gita (song of the Lord), usually called the Gita, is indubitably of the highest merit and the most popular. It is a part of the Bhishmaparvan.
The Gita has become in the last hundred and fifty years the subject of numerous editions, translations, commentaries and discussions.
Lokhamanya Tilak calls it " a most luminous and priceless gem which makes us masters of spiritual wisdom."
The oldest commentary available now is that of Adi Sankaracharya. Among the more famous bhashyas of post Sankara period are those of Ramanujacharya, Madhusudana Saraswathi and Sridhara.