Bukhari

Hadith Commentary:
Reciting the Zabur so quickly was a miracle (mu‘jizah) of Dawud (alayhis salam).
However, for ordinary Muslims, completing the Qur’an in less than three days is contrary to the Sunnah.
Whoever completes the Noble Qur’an in less than three days has not fulfilled the right of understanding the Qur’an.
Among his brothers, Dawud (alayhis salam) was of short stature, so people would look at him with disdain.
But Allah, the Exalted, granted Dawud (alayhis salam) superiority over his brothers and revealed the Zabur to him.
Thus, the phrase from the Injil (Gospel) became true: the stone which the builders rejected as faulty became the chief cornerstone of the palace.
Allah Ta‘ala granted Dawud (alayhis salam) the craft of working with iron as a miracle, such that iron would become soft like wax in his hands, and he would make coats of mail and various items from it.
This was his means of livelihood.
In the noble hadith, his fasting has also been praised, and in the Noble Qur’an, his worship, spiritual exercises, and turning to Allah have been described in a very beautiful manner.

Hadith Commentary:
The Zabur has been referred to as "Qur'an" because it contained a collection of rulings, or in the literal sense, because it was recited frequently. The ability to recite the Zabur so quickly was a miracle of Dawud (alayhis salam). However, in our Shari'ah, to complete the recitation of the Noble Qur'an in less than three days is contrary to the Sunnah.
According to the hadith, whoever completes the Noble Qur'an in less than three days has not fulfilled the right of understanding the Qur'an.
Dawud (alayhis salam) used to consume only from what he earned with his own hands.
His means of earning was that he would make iron armor and sell it.
Allah Ta'ala had made iron soft in his hands; he would prepare various items from it, and this was his means of livelihood.

Hadith Commentary:
The recitation of Dawud (alayhis salam) was as a miracle.
It is not permissible to complete the recitation of the Qur'an in less than three days.
The matter is different in the case of a karamah (miraculous occurrence granted to a saint).

Hadith Commentary:
➊
There were some admonitions, counsels, supplications, and glorifications in the Zabur, and for rulings, reliance was placed upon the Torah.
The fact that Dawud (alayhis salam) would recite the Zabur so quickly is a miracle.
Allah, exalted is He, folds up time for whomever He wills among His servants.
In the terminology of the Sufis, this is called "tayy al-zaman" (folding of time); an even more problematic term is "tayy al-makan" (folding of space). Then, under the cover of these terms, they have narrated such incidents that are contrary to reason and transmission.
➋
In any case, from this hadith it is understood that sometimes Allah, exalted is He, puts blessing in a short amount of time so that many tasks are accomplished within it.
And Allah knows best.