WajumiAAa ashshamsu walqamar (surah Qiyamah: 9)

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

(75:9) and the sun and the moon are joined together, *8

Wa jumi`ash shamusu wal qamar

*8) This is a brief description of the chaotic condition of the system of the universe, that will prevail in the first stage of Resurrection. The darkening of the moon and the joining of the moon and the sun together can also mean that not only will the moon lose its light, which is borrowed from the sun, but the sun itself will become dark and both will become devoid of light similarly. Another meaning can be that the earth will suddenly start rotating in the reverse order and on that day both the moon and the sun will rise simultaneously in the west. And a third meaning can be that the moon will suddenly shoot out of the earth's sphere of influence and will fall into the sun. There may possibly be some other meaning also of this which we cannot understand today.