And [by] the night when it covers it (91:4)

Almuntakhab Fi Tafsir Alquran Alkarim

By the night which keeps the sun out of view and the earth veiled to sight

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(91:4) and by the night as it envelopes the sun; *2

And [by] the night when it covers it meaning

*2) That is, when the night comes, the sun hides and its light remains hidden throughout the night. This state has been described, saying that the night covers up the sun, for the night actually signifies the sun's hiding behind the horizon because of which its light cannot reach that part of the earth where the night has fallen.
 

And [by] the night when it covers it meaning in Urdu

اور رات کی قسم جبکہ وہ (سورج کو) ڈھانک لیتی ہے