Oaths in old Arabic were usually said for no reason at all, [this has still continued today when our Arab/Somali friends begin their sentences with "wallahi"] Pre-Islam Oaths are also used to get attention. For example a caller would run to the top of a mountain, stand naked and swear by the next morning. Either the people would hear the oath and realise that something bad would happen the following morning or the people would see the crier naked and realise there is some sort of emergency. This was the mass media of that time. Prophet pbuh used the mass media but took the filth [standing naked] out of it. When he was commanded to spread the message of Islam to his people, he too climbed to the peak of a mountain and began by swearing an oath which caught the people's attention to gather round.
Oaths in the Qur'an vary through the surahs where Allah swt swears by time [surah 103], the sun [surah 91], the fig and the olive [surah 95]. Scholars have contended that whatever Allah swears by is important. Additionally Allah also used the oaths as a means of capturing the listener's attention. As we know there are 2 parts to an oath, the object and the subject of an oath. For example if someone says "I swear I did not see your ice-cream." The actual oath 'I swear' is the object and the latter part of the sentence is the subject. The object is there to get you ready for the subject, it is proof of the subject and it is a witness for the subject. In surah 103, Allah says 'By time, certainly man is in loss.'
A beautiful example of the use of oaths in the Qur'an to capture the listeners attention can be seen in Surah 100 - Surah al-'Aadiyaat. As the Qur'an was revealed in the rich language of Arabic and sent to a people who cherished their language, the Qur'an uses the oaths to capture their attention -something that was familiar to that society as well. Before we begin looking at the ayaat in the surah mentioned, it is important to note that whilst in that time the Arabs did not have access TV and film, their entertainment of that kind was captured in rich Arabic language in the form of poetry. In addition to this, the Arabs really took pride in their horse [it's the equivalent of a fast sports car for us today!] Therefore Allah swt grabs their attention immediately in the following verses of Surah al-'aadiyat in the form of powerful oaths.
Allah delivers the fast action of the horses in the form of a verbal movie trailer through the rhyme of the words in the ayaat. Below is a video of the impact the verses had on the listener then.
The trailer stops here, as this was the object to grab the attention of the listener. It only then dawns upon the listener what the message behind these verses is. The example given is that of the much loved animal, the horse and its loyalty to its master. But when it comes to your master, you are not as loyal to it, as the horse is to its master. SubhanAllah the lesson learnt from this and many more examples from the Qur'an really does show how universal the Qur'an really is.
[This post was a write up of my notes from Nouman Ali Khan's Divine Speech Seminar in London Dec 2011]