Quran, Chapter 16, Verse 94:
and do not make your oaths a means of deceit between youIn some verses of Quran, God almighty swears by different things to emphasize the importance of the topic. In one case, god almighty swears by the location of the stars and right after emphasizes on the importance of this oath. This is mentioned in the following verses:

Quran, Chapter 56, Verse 75-79:
I swear by the falling of stars, and most surely it is a very great oath if you only knew, most surely it is an honored quran, in a book that is protected, none shall touch it save the purified ones.In order to grasp the importance of this oath, one should know something about our immensely vast universe with its billions of galaxies and stars. Only in our galaxy there are about 500 billion stars. All of these stars move in a fixed orbit around the center of the galaxy. Considering these many stars moving with different speeds , it is very rare that two stars collide with each other. Swearing by the stars is also repeated in other verses of Quran:

Quran, Chapter 86, Verses 1-4:
I swear by the heaven and the comer by night, and what will make you know what the comer by night is? the star of piercing brightness; there is not a soul but over it is a keeper.

Quran, Chapter 53, Verses 1-4:
i swear by the star when it goes down, your companion does not err, nor does he go astray; nor does he speak out of desire, it is naught but revelation that is revealed.

Quran, Chapter 81, Verses 15-19:
but nay! I swear by the stars, that run their course (and) hide themselves, and the night when it departs, and the morning when it brightens, most surely it is the word of an honored messenger

In some verse of Quran, God almighty swears by the Quran itself:

Quran, Chapter 36, Verses 2-4:
I swear by the Quran full of wisdom, most surely you are one of the messengers, on a right way

Quran, Chapter 38, Verses 1-2:
suad, I swear by the Quran, full of admonition, nay! those who disbelieve are in self-exaltation and opposition

Quran, Chapter 43, Verses 2-3:
I swear by the book that makes things clear, surely we have made it an arabic quran that you may understand

Quran, Chapter 44, Verses 2-3:
I swear by the book that makes manifest (the truth), surely we revealed it on a blessed night surely we are ever warning

Here are some other verses of Quran in which God Almighty swears by other things:

Quran, Chapter 51, Verses 1-8:

I swear by the wind that scatters far and wide,

then those clouds bearing the load (of minute things in space),

then those (ships) that glide easily,

then those (angels who) distribute blessings by our command,

what you are threatened with is most surely true,

and the judgment must most surely come about,

I swear by the heaven full of ways,

most surely you are at variance with each other in what you say

Quran, Chapter 52, Verses 1-7:

I swear by the mountain,

and the book written

in an outstretched fine parchment,

and the house (kaaba) that is visited,

and the elevated canopy

and the swollen sea

most surely the punishment of your lord will come to pass

Quran, Chapter 91, Verses 1-7:

I swear by the sun and its brilliance,

and the moon when it follows the sun,

and the day when it shows it,

and the night when it draws a veil over it,

and the heaven and him who made it,

and the earth and him who extended it,

and the soul and him who made it perfect.

Quran, Chapter 100, Verse 1:
I swear by the runners breathing pantingly

Quran, Chapter 68, Verse 1:
noon. I swear by the pen and what the angels write

Quran, Chapter 95, Verses 1-4:
I swear by the fig and the olive, and mount Sinai, and this city made secure, certainly we created man in the best make.