“Fasting and the Qur’ān shall intercede for the servant on the Day of Resurrection. Fasting will say: ‘O Lord, I prevented him from food and desires during the day, so allow me to intercede for him.’ And the Qur’ān will say: ‘I prevented him from sleep at night, so allow me to intercede for him.’ He said: ‘Then they shall be permitted to intercede.’”

Narrated by Aḥmad (no. 6626, the wording is his), al-Ḥākim (no. 2036), al-Ṭabarānī in al-Kabīr (no. 88), and al-Bayhaqī in Shuʿab al-Īmān (no. 1839), from the ḥadīth of ʿAbd Allāh ibn ʿAmr—may Allah be pleased with them both.
Authenticated in Ṣaḥīḥ al-Jāmiʿ (no. 3882) and Ṣaḥīḥ al-Targhīb wa al-Tarhīb (no. 984).

Brief Explanation of the Hadith

Among the righteous deeds are those that serve as a means of intercession for the servant on the Day of Resurrection, an intercession that Allah, the Exalted, accepts. Among these are fasting and the Qur’ān, when performed in the manner that pleases Allah, the Exalted.
Fasting, when mentioned generally, refers primarily to the fasts of the month of Ramadān; and if voluntary fasts are added to it, this constitutes a more complete state and yields a greater share of reward. As for the Qur’ān, it refers to its recitation at night while people are asleep, whether the recitation is within prayer or outside of it.
Fasting bears witness for the servant that he has restrained himself from food and desires in obedience to Allah, and the Qur’ān bears witness that he has restrained himself from sleep at night in prayer and recitation. They both ask Allah to accept their intercession for him, and Allah, the Exalted, allows them to intercede.
And in His statement, “Fasting will say… and the Qur’ān will say,” is an indication that Allah, the Exalted, gives deeds a form of personification on the Day of Resurrection, granting them speech and testimony. Likewise, some of the limbs of the servant are given a tongue that speaks and bears witness against or for its owner, just as Death is brought in the form of a ram and is slaughtered between Paradise and Hell.
The wisdom in mentioning fasting and the Qur’ān together in this ḥadīth is explained by the fact that fasting is often accompanied by night prayer and recitation of the Qur’ān, so they are paired both in action and in intercession. This intercession indicates the great status of fasting and night prayer, and their immense effect on the Day of Resurrection.