In the Hari-vamsha it is stated;
vede ramayane caiva purane bharate tatha
adavante ca madhye ca harih sarvatrah giyate
“In all the Vedas, Ramayana, Puranas and Mahabharata, Lord Hari’s glories are sung throughout within the beginning, middle, and therefore the end.”
The Bhagavad-gita is one of the sections of the Bhishma Parva of the Mahabharata, thus it is scripture. Scriptures are narrations about the Supreme Lord or words spoken by the Supreme Lord. Shrimad-Bhagavatam is a beautiful narration of the pastimes of the Supreme Lord and Bhagavad-gita is the song of the Supreme Lord Krishna. Both are non different from Him.
Benefits Of Bhagavat Gita recital:
From the Hari-bhakti-vilasa 6.214-228) :
salagrama-silagre tu gitadhyayam pathet tu yah
manvantara-sahasrani vasate brahmanah pure
One who recites a chapter from the Bhagavad-gita ahead of a shalagrama-shila resides for thousand manvantaras in Lord Brahma’s abode.
tenestam kratubhih sarvair dattam tena gavayutam
gitam abhyasyata nityam tenaptam padam avyayam
Such an individual attains the results of donating ten thousand cows and therefore the results of conducting all Vedic sacrifices. Those who constantly study the Bhagavad-gita attain to the eternal unseen .
yo nityam visva-rupakhyam adhyayam pathati dvijah
vibhutim deva-devasya tasya punyam vadamy aham
A brahmin who studies the tenth and eleventh chapter of the Bhagavad-gita attains the subsequent result [as described within the next verse].
vedair adhitair yat punyam setihasaih puratanaih
slokenaikena tat punyam labhate natra samsayah
abrahma-stamba-paryantam jagat-trptim karoti sah
visva-rupam sadadhyayam vibhutim ca pathet tu yah
By studying one verse from these two chapters one attains an equivalent result as studying all the Vedas, Itihasas and Puranas, of which there's little question . One who studies the tenth and eleventh chapters enjoys all pleasures enjoyed by all living entities — from the standard blades of grass up to Lord Brahma.
ahany ahani yo martyo gitadhyayam pathet tu vai
dvatrimsad-aparadhams tu ksamate tasya kesavah
Lord Keshava forgives all thirty-two sorts of offenses for a mortal who recites a chapter of the Bhagavad-gita.
likhitva vaisnavanam ca gita-sastram prayacchati
dine dine ca yajate harim catra na samsayah
There is little question that those that copy and gift this literature to the devotees of the Lord attain an equivalent result as worshiping Lord Hari daily.
caturnam eva vedanam saram uddhrtya visnuna
trailokyasyopakaraya gita-sastram prakasitam
For the advantage of the three worlds, Lord Vishnu has extracted the essence of the four Vedas and manifested that essence within the sort of the literature referred to as Bhagavad-gita.
bharatamrta-sarvasvam visnor vaktrad vinihsrtam
gita-gangodakam pitva punar janma na vidyate
Everything within the Mahabharata has emanated from the mouth of Lord Vishnu. Those who drink the Ganges-like water of the Bhagavad-gita don't take birth again within the material world.
yo narah pathate nityam gita-sastram dine dine
vimuktah sarva-papebhyo yati visnoh param padam
The one that constantly reads the Bhagavad-gita day after day gets liberated from all sins and attains Lord Vishnu’s abode.