Tafsir of Al-Burooj 85:7

This means that some of them would bear witness to others before the king that no one had fallen short in what they were commanded to do, or they would bear witness before him regarding the excellence of what they were doing and how it contained—according to what has been said—righteousness. Or, some would bear witness against others regarding this heinous act on the Day of Resurrection, or they would bear witness against themselves regarding it on the day when their limbs testify against them concerning their deeds.

It has been said that "over" (‘ala) carries the meaning of "with" (ma‘a). The meaning then is: They were present with the torment they were inflicting upon the believers, showing them no mercy due to the extreme hardness of their hearts.

As for those who claim that Allah, the Exalted, saved the believers and that He, the Exalted, only burned the disbelievers, they say that what is intended here is: "And they were witnesses over what they wanted to do to the believers." Regardless of the interpretation, the term "the believers" involves the dominance of the masculine, and the intent is both believing men and believing women.

Among the oddities that should be disregarded is the claim that the People of the Trench were ‘Amr ibn Hind—who was known as al-Muharriq (the Burner)—and those with him, who burned one hundred men of Banu Tamim, and that the pronoun in "what they did" refers to the disbelievers of Quraysh who were persecuting the believing men and women.