Linkage with the preceding Surah
This Surah mostly contains subjects relating to the Day of Judgment, Resurrection, the Reckoning, Paradise, the Fire, Allah's reward and punishment etc. Thus this Surah is linked with Surah Al-Hujurat because the concluding part of the latter Surah dealt with these subjects.
Characteristics and Virtues of Surah Qaf
It is reported in Muslim, as cited in Qurtubi, that Umm Hisham Bint Harithah Ibn Nu` man ؓ ، said: "For around two years, or a year and a part of another year, we shared one single oven with the Holy Prophet ﷺ . I memorized Surah Qaf from the Holy Prophet ﷺ who used to recite it every Friday while standing on the pulpit delivering the Friday sermon to the people."
Sayyidna ` Umar Ibn-ul-Khattab ؓ asked Abu Waqid Al-Laithi: "What did the Holy Prophet ﷺ recite during the ` Id prayers?" He replied: "Surah Qaf and Surah Qamar." Sayyidna Jabir ؓ reports that the Holy Prophet ﷺ used to recite Surah Qaf often in the Morning Prayer. (Despite that this Surah is rather long,) the prayer was felt light (Qurtubi). It was the special trait of the recitation of the Holy Prophet ﷺ that praying behind him caused no stress, even when he recited the long Surahs.
Is it Possible to Observe the Heaven?
أَفَلَمْ يَنظُرُوا إِلَى السَّمَاءِ (Did they not, then, look to the sky above them? - 50:6). Apparently this sentence indicates that it is possible to see the sky, while the general impression is that the blue colour that we see above is the colour of the atmosphere, and not that of the heaven. However, there is no proof for non-existence of the sky, nor of the presumption that the colour of the heaven is not blue. Besides, the word nazar (seeing) used in the verse could mean perceiving through reason, that is, thinking, pondering etc. (Bayan-ul-Qur’ an)