gita-shastram idam punyam, yah pathet prayatah puman
vishnoh padam avapnoti, bhaya-shokadi-varjitah.
If one properly follows the instructions of Bhagavad-gita, one can be freed from all miseries and anxieties in this life, and one’s next life will be spiritual.
(Gita-mahatmya 1)

There is also a further advantage:

gitadhyayana-shilasya, pranayama-parasya ca
naiva santi hi papani, purva-janma-kritani ca

“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.”
(Gita-Mahatmya 2)

The Lord says very loudly in the last portion of Bhagavad-gita (18.66):

sarva-dharman parityajya
mam ekam sharanam vraja
aham tvam sarva-papebhyo
mokshayishyami ma sucah

“Abandon all varieties of religion and just surrender unto Me. I shall deliver you from all sinful reactions. Do not fear.” Thus the Lord takes all responsibility for one who surrenders unto Him, and He indemnifies such a person against all reactions of sins.

maline mocanam pumsam, jala-snanam dine dine
sakrid gitamrita-snanam, samsara-mala-nashanam

“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-gétä, for him the dirt of material life is altogether vanquished.”
(Gita-Mahatmya 3)

gita su-gita kartavya, kim anyaih shastra-vistaraih
ya svayam padmanabhasya, mukha-padmad vinihsrita

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-gétä, will suffice, because it is the essence of all Vedic literatures and especially because it is spoken by the Supreme Personality of Godhead.
(Gita-Mahatmya 4)
As it is said:
bharatamrita-sarvasvam, vishnu-vaktrad vinihsritam
gita-gangodakam pitva, punar janma na vidyate

“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 Krishna Himself, the original Vishnu.”

(Gita-Mahatmya 5) Bhagavad-gétä comes from the mouth of the Supreme Personality of Godhead, and the Ganges is said to emanate from the lotus feet of the Lord. Of course, there is no difference between the mouth and the feet of the Supreme Lord, but from an impartial study we can appreciate that Bhagavad-gita is even more important than the water of the Ganges.

sarvopanishado gavo, dogdha gopala-nandanah
partho vatsah su-dhir bhokta, dugdham gitamritam mahat

“This Gitopanishad, Bhagavad-gita, the essence of all the Upaniñads, is just like a cow, and Lord Krishna, 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”
(Gita-mahatmya 6)

ekam shastram devaki-putra-gitam
eko devo devaki-putra eva
eko mantras tasya namani yani
karmapy ekam tasya devasya seva
(Gita-mahatmya 7)
In this present day, people are very much eager to have one scripture, one God, one religion, and one occupation.
Therefore, ekam shstram devaki-putra-gitam: let there be one scripture only, one common scripture for the whole world-Bhagavad-gita.
Eko devo devaki-putra eva: let there be one God for the whole world-Sri Krishna. Eko mantras tasya namani: and one hymn, one mantra, one prayer—the chanting of His name: Hare Krishna Hare Krishna Krishna Krishna Hare Hare Hare Rama Hare Rama Rama Rama Hare Hare. Karmapy ekam tasya devasya seva: and let there be one work only—the service of the Supreme Personality of Godhead.