Tanaffas liturally means to breaths but here it means to become bright (the morning) i.e when the light of the day comes out.
As to what has been mentioned so far, is there a connection? When Allah speaks about starts in the Qur’an, He says they are there for an adornment but also as a guide for those on earth. Humans can use stars as a guide to know which direction they are heading. So you can tell your geographical location on earth by the position of the starts.
When its dark its hard to see what is ahead of you but as soon as day light approaches you can now see a bit better and when the daylight becomes complete you can now see perfectly ahead of you.
So it that what has been mentioned so far (verse 15-18) is connected to the concept of guidance. So Allah is swearing by those things that give guidance as if to indicating that If Allah has given man so many means to be guided in worldly matters then for sure He will also give man the means to be guided in the religious matters.
So what are the Jawaab (responses) to all of these oaths? The next verse is the answer.
ContemplateQuran 