Tafsir of Ad-Dhariyat 51:34

(Marked): Signified; derived from al-sawma, which is the mark. Upon each of them is the name of the one to be destroyed by it. It is also said: They were marked to indicate they are stones of punishment. It is also said: Marked with a sign indicating they are not of the stones of this world. It is also said: Musawwamah means sent forth, from "letting camels pasture" (asmat al-ibil), as in His saying, the Exalted: "And from it is the tree in which you pasture (tusimun)."

(By your Lord): That is, at the place of the manifestation of His power, glory, and majesty—Exalted and Majestic is He. The intended meaning is that they were marked at the beginning of their creation. It is also said that the meaning is that they are prepared in the knowledge of Allah, the Exalted, (for the extravagant): those who exceed the limits in wickedness. The definite article (al) here, according to the Imam, denotes specific reference (lil-‘ahd), meaning: for these specific extravagant ones. The explicit noun was placed in the stead of the pronoun to condemn them for their extravagance, following their condemnation for their crimes, and to point toward the ratio legis (the reason for the judgment).