And [a sign too] in Moses (wa-fī Mūsā is a supplement to fīhā, ‘therein’), that is to say, We also left a sign in the story of Moses, when We sent him to Pharaoh, vested, with a clear warrant, with a manifest proof;
(And in `Ad when We sent against them the barren wind) that destroys everything and produces nothing. This was said by Ad-Dahhak, Qatadah and others. Allah's statement,
مَا تَذَرُ مِن شَىْءٍ أَتَتْ عَلَيْهِ
(It spared nothing that it reached,) meaning, everything that the wind could destroy,
إِلاَّ جَعَلَتْهُ كَالرَّمِيمِ
(but blew it into broken spreads of rotten ruins.) meaning, made it just like a rotten and destroyed. Sa`id bin Al-Musayyib and others commented on:
إِذْ أَرْسَلْنَا عَلَيْهِمُ الرِّيحَ الْعَقِيمَ
(when We sent against them the barren wind),"Southerly winds.'' However, there is a Hadith in the Sahih from Shu`bah bin Al-Hakam, from Mujahid, from Ibn `Abbas, who said that the Messenger of Allah said,
(And in Thamud, when they were told: "Enjoy yourselves for a while!'' But they insolently defied the command of their Lord, so the Sa`iqah overtook them while they were looking.) Thamud were given a respite for three days, during which they await the torment. In the early morning of the fourth day, the torment overtook them,
فَمَا اسْتَطَـعُواْ مِن قِيَامٍ
(Then they were unable to rise up,) they were unable to escape and run away from it,
وَمَا كَانُواْ مُنتَصِرِينَ
(nor could they help themselves.) nor could they save themselves from the torment that befell them. Allah the Exalted and Most Honored said,
وَقَوْمَ نُوحٍ مِّن قَبْلُ
((So were) the people of Nuh before them.) meaning, `We destroyed the people of Nuh before these people (Fir`awn, `Ad and Thamud).'
إِنَّهُمْ كَانُواْ قَوْماً فَـسِقِينَ
(Verily, they were a people who were revellious.) We mentioned these stories in details before in the Tafsir of several other Surahs.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
"A clear authority': such miracles and clear evidences which made it absolutely manifest that he had been appointed as a Messenger by the Creator of the earth and heavens.
That is, they called him sometimes a sorcerer and sometimes a madman.
A whole history has been compressed into this brief sentence. To understand it well one should know that Pharaoh was the absolute ruler of the greatest center of civilization and culture of the world in those days and the people of the adjoining lands were overawed by his power and might. Obviously, when he might have sunk suddenly one day in the sea along with his armies, the event must have become well known not only in Egypt but among all the neighboring nations as well. At this, except for those whose kith and kin had sunk, there was no one else among their own people, or in the other nations of the world who would mourn them or write an elegy on them, or would at least express sorrow and say that good and noble people had become a victim of the disaster. Instead of this, as the world had become fed up with their wickedness and injustices, every person heaved a sigh of relief at their exemplary fate, everyone cursed them, and anyone who heard this news exclaimed that the wicked people had deserved the fate justly. In Surah Ad-Dukhan the same thing has been expressed, thus: "Then neither did the heavens weep on them nor the earth." (For explanation, see E.N. 26 of Surah Ad-Dukhan).