Abdullah bin Abbas reported,
The entire Quran was sent down all at once on Laylat al-Qadr in Ramadan to the lowest heaven. Then, whenever Allah willed to bring something about on earth, He would send down a portion of it, until it was completed in full.
Azami 664
Sahihعن ابن عباس، قال
نزل القرآن كله جملة واحدة في ليلة القدر في رمضان إلى السماء الدنيا، فكان الله إذا أراد أن يحدث في الأرض شيئا أنزله منه حتى جمعه.
No references are available.
Ibn Jareer Tabari narrated it in his Tafsir (24/542), and Hakim (2/222), and from him Bayhaqi in al-Asma wal-Sifat (498), from Ibn Muthanna, who said, Abdul-Ala narrated to us, who said, Dawud narrated to us, from Ikrima, from Ibn Abbas, and he mentioned it.Ibn Muthanna is Muhammad bin Muthanna bin Ubayd Anazi, who died in the year 252 AH. Hakim said, "Sahih in isnad."