Tafsir of Ad-Dhariyat 51:44

(So they were insolent toward the command of their Lord) i.e., they acted with arrogance against complying with it until the end. The fa (so) is for detailing. It is stated in al-Kashf that this is the apparent meaning in this context, as is His saying—Exalted is He—(But he turned away with his forces [birkinihi]), which is ordered upon the story at the time Moses—peace be upon him—was sent with the authority. Even if there is no obstacle to it being ordered upon the sending, this is because the adverbial phrase (zharaf) was introduced as a supplementary element, as the sign and the story of their turning away were placed within it, up to their destruction.

Al-Hasan said: This, meaning [the statement] "Enjoy yourselves for a time," occurred when Salih was sent to them; they were commanded to believe in what he brought and to enjoy themselves until their appointed terms arrived, then they became insolent after that. It is stated in al-Bahr: For this reason, the conjunction with fa came, which necessitates that the insolence occurred after they were commanded, so it is consistent in wording and existence. The Imam chose this, saying: Some exegetes said the intended meaning of "the time" is the three days they were granted respite after the hampering of the she-camel. This is weak because the ordering of "so they were insolent" with fa is proof that the insolence was after the aforementioned statement. Thus, the apparent meaning is that which God Almighty has ordained of the appointed terms; there is no one who is not granted respite for the duration of their term, as if He is saying to him: "Enjoy yourself until the end of your term." If you do good, you have attained enjoyment in both abodes, and if not, then you have no portion in the Hereafter. What preceded is more profound in meaning.

(So the thunderbolt seized them) i.e., it destroyed them. It is narrated that Salih—peace be upon him—promised them destruction after three days and said to them: "Tomorrow your faces will become yellow, the day after red, and on the third day black; then the punishment will reach you." When they saw the signs that he—peace be upon him—had explained, they attempted to kill him, but God saved him, and he departed to the land of Palestine. When it was the forenoon of the fourth day, they embalmed themselves and shrouded themselves in leather mats; then the thunderbolt came upon them—which is fire from the sky, and it is said it was a shout from it—so they perished. Omar, Uthman—may God be pleased with them—and al-Kisa'i read it as as-sa'qah, which is the single instance of sa'q (to strike/thunder), meaning also the thunderbolt or the shout.

(While they were looking on) at it and witnessing it. It is necessary to treat the heard as the seen if one adopts the view that the thunderbolt was a shout, and that what is meant by "looking on" is looking at it. Mujahid said: "Looking on" means waiting; which is to say, they were waiting for the seizure and the punishment during those three days in which they saw its signs, and waiting for the punishment is more intense than the punishment itself.