Tafsir of Al-Mujadilah 58:21

"Allah has decreed: 'I shall surely overcome, I and My messengers.'"

(Allah has decreed) is a commencement brought forth to provide the cause for them being among the abased; meaning: He has established it in the Preserved Tablet, or He has ordained and judged it. Qatadah said: In either case, it functions in the manner of an oath. Hence, the Glorified said: (I shall surely overcome, I and My messengers) — meaning by argument, by the sword, and that which follows the same course, or by one of the two. In regard to overcoming by means other than argument, it suffices that it was realized for the messengers—peace be upon them—in their times, mostly. For the Glorified destroyed many of their enemies with various types of punishment, such as the people of Nuh, the people of Salih, the people of Lut, and others. Although the war between our Prophet—may Allah bless him and grant him peace—and the polytheists was back and forth, the final outcome belonged to him—upon him be peace and prayer. Likewise, it is promised to their followers; however, this is when their jihad against the enemies of the religion is like the jihad of the messengers against them—in that it is purely for Allah, the Mighty and Majestic, and not for the sake of seeking dominion, authority, or worldly objectives. You will hardly find a mujahid of such a character who is not, for the most part, granted victory.

Some have restricted this overcoming to "argument" due to its consistency, but this is contrary to the apparent meaning and is made improbable by the context of the revelation. For Muqatil reported that when Allah, the Exalted, granted the believers victory over Makkah, Ta'if, Khaybar, and their surroundings, they said: "We hope Allah, the Exalted, will grant us victory over Persia and Rome." Abdullah ibn Ubayy then said: "Do you think Rome and Persia are like some of the villages you have overcome? By Allah, they are greater in number and more severe in might than those you think of in that way." Then this was revealed: (Allah has decreed: 'I shall surely overcome, I and My messengers.') (Indeed, Allah is Powerful) over granting victory to His messengers, (Mighty) - (He is not overcome in His will, the Exalted).

Nafi' and Ibn 'Amir read wa rusuli (and My messengers) with a fatha on the ya.