Exegesis of the saying of Allah the Exalted: "Master of the Day of Judgment": The wisdom in specifying Allah's ownership of the Hereafter, even though He is the Master of both the worldly life and the Hereafter.

"Master" is an attribute of the Lord, and is the Day of Resurrection, and here means what? It means recompense, meaning that He, Glorified and Exalted is He, is the Master of that day in which the creation are recompensed, so there is no Master other than Him on that day.
If someone were to ask: Is He not the Master of the religion and the worldly life? The answer is: Yes, but the manifestation of His lordship, ownership, and authority is specifically on that day, because Allah the Exalted calls out: "To whom does the kingdom belong today?" No one answers, so He says: "To Allah, the One, the Subduer." In the worldly life, kings appear, and indeed kings appear who their peoples believe are the only ones with ownership, so the communists, for example, do not see that there is a Lord of the heavens and the earth; they see it as a life where wombs give birth and the earth swallows, and that their Lord is their president. So, He specified His ownership with the Day of Judgment because His lordship and ownership are manifested in it.