Krsna Dvaipayana Vyasa has written this song “Gita Sastram Idam Punyam”. The official name of this song is Gita Mahatmya. This song is taken from the book Padma Purana. In this song, the benefits of reading Bhagavad Gita are elaborated.
gita-sastram idam punyam yah pathet prayatah puman
visnoh padam avapnoti bhaya-sokadi-varjitah
gitadhyayana-silasya pranayama-parasya ca
naiva santi hi papani purva-janma-krtani
maline mocanam pumsam jala-snanam dine dine
sakrd-gitambhasi snanam samsara-mala-nasanam
gita sugita kartavya kim anyaih sastra-vistaraih
ya svayam padmanabhasya mukha-padmad vinihsrta
bharatamrta-sarvasvam visnor vaktrad vinihsrtam
gita-gangodakam pitva punar-janma na vidyate
sarvopanisado gavo dogdha gopala-nandanah
partho vatsah sudhir bhokta dugdham gitamrtam mahat
ekam sastram devaki-putra-gitam
eko devo devaki-putra eva
eko mantras tasya namani yani
karmapy ekam tasya devasya seva
(1) If one properly follows the instructions of Bhagavad-gita, one can be freed from all the miseries and anxieties of life. One will be freed from all fears in this life, and one's next life will be spiritual.
(2) If one reads Bhagavad-gita very sincerely and with all seriousness, then by the grace of the Lord the reactions of his past misdeeds will not act upon him.
(3) One may cleanse himself daily by taking a bath in water, but if one takes a bath even once in the sacred Ganges water of Bhagavad-gita, for him the dirt of material life is altogether vanquished.
(4) Because Bhagavad-gita is spoken by the Supreme Personality of Godhead, one need not read any other Vedic literature. One need only attentively and regularly hear and read Bhagavad-gita. In the present age, people are so absorbed in mundane activities that it is not possible for them to read all the Vedic literatures. But this is not necessary. This one book, Bhagavad-gita, will suffice, because it is the essence of all Vedic literatures and especially because it is spoken by the Supreme Personality of Godhead.
(5) One who drinks the water of the Ganges attains salvation, so what to speak of one who drinks the nectar of Bhagavad-gita? Bhagavad-gita is the essential nectar of the Mahabharata, and it is spoken by Lord Krsna Himself, the original Visnu.
(6) This Gitopanisad, Bhagavad-gita, the essence of all the Upanisads, is just like a cow, and Lord Krsna, who is famous as a cowherd boy, is milking this cow. Arjuna is just like a calf, and learned scholars and pure devotees are to drink the nectarean milk of Bhagavad-gita.
(7) Let there be one scripture only, one common scripture for the whole world — Bhagavad-gita. Let there be one God for the whole world — Sri Krsna. Let there be only one hymn, one mantra, one prayer — the chanting of His name: Hare Krsna, Hare Krsna, Krsna Krsna, Hare Hare/ Hare Rama, Hare Rama, Rama Rama, Hare Hare. Let there be one work only — the service of the Supreme Personality of Godhead.