As-Sajdah 32:25 - Linguistic Miracle

“Indeed, your Rabb, He alone will separate between them on the day of resurrection concerning that over which they used to differ.

The reason He uses the word Rabb is tied to the previous verse where Allah promised the Muslims victory and leadership if they remain steadfast. He follows that promise by calling Himself the Rabb of the prophet ﷺ to say that He will indeed take care of you, give you victory, be your helper, and protect you from the disbelievers until His promise comes.

He alone- The extra pronoun هو creates the meaning of exclusivity. Allah alone, and no one else will judge between them. The God who has promised to help you and give you victory, He alone will judge between them. They will be at the mercy of the one who loves you. Therefore, anyone who opposes you, or tries to harm you, will meet his punishment with Him.

The disbelievers will become believers on judgment day, but Allah will separate them from those who believed while they were alive on the earth. Those who believe while in this world, will not be treated the same as those who believe only when they see it in reality on judgment day. Allah will divide them, He will treat them as two separate groups, not as one.

Concerning that over which they used to differ - the differences between the believers and the disbelievers that have come in this surah.