Verse 125 in Al-an'aam

 فَمَن يُرِدِ ٱللَّهُ أَن يَهۡدِيَهُ ۥ يَشۡرَحۡ صَدۡرَهُ ۥ لِلۡإِسۡلَـٰمِ‌ۖ وَمَن يُرِدۡ أَن يُضِلَّهُ ۥ يَجۡعَلۡ صَدۡرَهُ ۥ ضَيِّقًا حَرَجً۬ا ڪَأَنَّمَا يَصَّعَّدُ فِى ٱلسَّمَآء

And whomsoever Allâh wills to guide, He opens his breast to Islâm/submission, and whomsoever He wills to send astray, He makes his breast closed and constricted, as if he is climbing up to the sky. .[] (125) 

This verse is fairly powerful. It is self explanatory, yet at the same time, on point. Whoever God chooses to be guided, He will instill a sense of comfort in their chest/heart and they will be of those who submit their will to God alone. On the contrary, those who God chooses to be strayed will not have the sense of comfort instilled in them, but rather their chest/heart will feel constricted and trapped. Next in the verse, God gives us an example of how this person will be. It will be as if he is going up to the sky. Now, how does that make sense? What does going up to the sky have to do with feeling uncomfortable? Think about it. Scientifically speaking, the more you go up, the more what happens? The more you lose oxygen, thus making your breathing more and more difficult. It is fair to say that the more someone goes up, the more he/she is uncomfortable and constricted.  

Look at how on-point God is in this verse? I would never have correlated the two together on my own without thinking about it. There is a profound reason for every example of God’s words that can be proven in our day and age. Even science cannot deny the truth that lay in this analysis of the sky given by our wise and just God.

Below is a brief description of how our oxygen changes as our altitude increases by Answers.com:

“If you think about it, you can understand that the amount of oxygen in the air becomes less as your altitude increases. With each breath, you get less O₂ to keep you conscious and alive. And as you consider this, you can probably figure out that altitude affects people differently. There is what is called a thresholdfor the medical condition called altitude sickness (acute mountain sickness) that begins at about 8,000 feet, or about 2,400 meters. Blood chemistry changes in response to decreasing air pressure as we gain altitude. The process is a bit involved, it's complex, and it takes a bit of study. And it's not all about justthe oxygen. It's the law of partial pressures of gases and (more importantly) the pathophysiological response.”