"And they were followed"—they were pursued—"by a curse in this world," meaning the torment with which He punished them, "and on the Day of Resurrection," meaning: and they shall also have a curse on the Day of Resurrection; that is, the punishment of Hellfire. "Verily, 'Ad, the people of Hud, were far away (distanced from mercy)."
Muhammad said: "Bu'dan" (remoteness/distance) is in the accusative case (mansub) based on the meaning: "May Allah distance them," so they were distanced a great distancing; meaning: from the mercy of Allah.