Tafsir of Al-Burooj 85:3

It means: and those among the created beings who will be resurrected who witness that Day and attend it, along with the terrors and wonders that will be present therein. Thus, Allah (Exalted and Majestic is He) has sworn by the Day of Resurrection and what it contains, in order to magnify that Day and strike terror into those who deny it.

The indefinite nature of these two descriptions is for magnification; that is, a "witness" and a "witnessed" whose descriptions cannot be fully encompassed, or it is for multiplication, as was said regarding the verse: "And every soul shall know what it has brought [with it]."

Al-Tirmidhi and a group have narrated from Abu Hurayrah (in a marfu’ tradition): "The witness is the day of Friday, and the witnessed is the day of ‘Arafah." This was also narrated in a marfu’ tradition from Abu Malik al-Ash'ari and Jubayr ibn Mut'im (may Allah be pleased with them). A group also narrated it from Ali (may Allah honor his face) and other Companions and Successors. Al-Hakim recorded it, and authenticated it, as a marfu’ tradition from him as well: "The witness is the day of ‘Arafah and the day of Friday, and the witnessed is the Day of Resurrection."

‘Abd ibn Humayd and Ibn al-Mundhir narrated from Ali (may Allah honor his face): "The witness is the day of Friday, and the witnessed is the day of the Star (al-Najm)."

Ibn Jarir and Ibn Marduyah narrated from al-Hasan ibn Ali (may Allah be pleased with them both): A man asked him about this, so he asked, "Have you asked anyone before me?" The man replied, "Yes, I asked Ibn Umar and Ibn al-Zubayr." They both said: "The day of Sacrifice (al-Dhabh) and the day of Friday." He said, "No; rather, the 'witness' is Muhammad (may Allah bless him and grant him peace)," and in one narration: "my grandfather, the Messenger of Allah (may Allah bless him and grant him peace)." Then he recited: "And We will bring you, [O Muhammad], as a witness against these." And the "witnessed" is the Day of Resurrection, then he recited: "That is a Day for which the people are gathered, and that is a Day witnessed."

Al-Nasa'i and a group narrated something similar from Ibn Abbas (may Allah be pleased with them both) through various chains.

‘Abd ibn Humayd, Ibn al-Mundhir, and Ibn Abi Hatim narrated from him: "The witness is Allah (Exalted and Majestic is He), and the witnessed is the Day of Resurrection."

From Mujahid, ‘Ikrimah, and ‘Ata’ ibn Yasar: "The witness is Adam (peace be upon him) and his offspring, and the witnessed is the Day of Resurrection."

From Ibn al-Musayyib: "The witness is the day of Tarwiyah, and the witnessed is the day of ‘Arafah."

From al-Tirmidhi: "The witness is the Recording Angels (al-Hafazah), and the witnessed is that which the people bear witness to."

From ‘Abd al-‘Aziz ibn Yahya: "They are the Messenger of Allah (may Allah bless him and grant him peace) and his nation (peace and blessings be upon him)." And from him also: "They are the Prophets (peace be upon them) and their nations."

From Ibn Jubayr and Muqatil: "They are the limbs and their owners."

It is also said: They are the day of Monday and the day of Friday. It is said: They are the alternating angels (peace be upon them). It is said: They are the Qur'an and the dawn. It is said: They are the star, the night, and the day. It is said: The witness is Allah (Exalted is He), the angels, and those of knowledge; the witnessed is His Oneness, and that the religion with Allah is Islam. It is said: The witness is His creations, and the witnessed is the Oneness. It is said: They are the Black Stone and the pilgrims. It is said: They are the nights, the days, and the sons of Adam. For al-Hasan said: "There is no day but that it cries out: 'I am a new day, and I am a witness to what is done upon me, so take advantage of me; for if my sun sets, you will not grasp me until the Day of Resurrection.'"

It is said: The nation of the Prophet (may Allah bless him and grant him peace) and the rest of the nations. It is permitted that they refer to the near ones (al-muqarrabūn) and the exalted ones (al-‘illiyyūn), due to His saying: "A register inscribed, which those near [to Allah] witness." And it is permitted that the witness be the infant who said, "O mother, have patience, for you are upon the truth," as will come later, if Allah wills, and the witnessed is his mother and the believers, because if his mother is upon the truth, then the rest of the believers are likewise.

There are about thirty opinions regarding this that I have encountered. The description in some of them refers to witnessing in the sense of "presence," the opposite of being absent. In others, it refers to testifying against an adversary, or it is the testimony of the limbs, which Allah (who makes all things speak) will cause to speak; likewise the Black Stone. There is nothing far-fetched in its presence on the Day of Resurrection to testify for the pilgrims.

As for the testimony of "the Day," it is possible that it occurs after it appears in a form, like the appearance of the Qur'an in the form of a pale man as he meets his companion when he rises from his grave, and the appearance of Death in the form of a ram on the Day of Resurrection until it is slaughtered between Paradise and Hell, among other such instances.

Al-Shihab said: Allah (Exalted is He) is capable of causing the Day to be present so that it may witness, but the method of this has not been clarified. If it is as we mentioned, then that is it; and if it is something else—such as the Day itself being present on that day—then the apparent implication is that "time" must have a "time," which, although permitted by some of the dialectical theologians, remains obscure regarding testimony via verbal speech. Similar to this is the "calling out" of the Day which I heard just now from al-Hasan, if it is by verbal speech rather than the language of state (lisān al-hāl), as is more likely in my view.

Abu Hayyan chose from the opinions—assuming that "witnessing" is understood in the second sense—that the "witness" is the one who bears witness on that Day, meaning the Promised Day of Resurrection, and that the "witnessed" is the one who is testified against on it. And assuming that it is understood in the first sense, the opinion is that the "witness" is the creations present for the reckoning, and the "witnessed" is the Day itself. Perhaps the repetition of the oath by it, even if the title differs, is for the sake of its increased magnification; so reflect.

As for the answer to the oath, it is said to be His saying: "Indeed, those who tormented..." Al-Mubarrad said it is His saying: "Indeed, the assault of your Lord is severe." Ibn Jurayj explicitly stated this, and Ibn al-Mundhir and al-Hakim recorded—and authenticated—from Ibn Mas'ud that which points to it. Many others have said it is His saying: [...]