Surah al-Qadr

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: The Qur'an was sent down all at once to the lowest heaven in the month of Ramadan, on the Night of Decree (Laylat al-Qadr), and then from there it was sent down in separate portions.
Al-Tabarani recorded it in al-Mu'jam al-Awsat and al-Mu'jam al-Kabir; its chain contains Imran al-Qattan, whom Ibn Hibban and others declared thiqah (trustworthy), though there is weakness in him; the rest of its narrators are thiqat (trustworthy).

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said concerning this statement of Allah Almighty (Allah Almighty says): "Indeed, We sent it down on the Night of Decree." Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: The Qur'an was sent down all at once until it was placed in the House of Honour (Bayt al-Izzah) in the lowest heaven; then Sayyiduna Jibril (peace be upon him) kept bringing it down to Sayyiduna Muhammad (peace and blessings be upon him) in accordance with the response to the words and deeds of the people.
Al-Tabarani recorded it, and al-Bazzar recorded it in abridged form. The narrators of al-Bazzar are the narrators of the Sahih, and the chain of al-Tabarani contains Amr bin Abd al-Ghaffar, who is da'if (weak).