In Short: When Allâh the Most High deposited the faculty of will (Juz' ikhtiyâri) in man and made him the source (masdar - lit. verbal noun, infinitive) of the world of actions, He sent His word (kalâm) in order to set that world in order.

The positioning [with respect to the preceding phrase] of the phrase "Now, as for those who have attained to faith, they know that it is the truth from their Lord and Sustainer (fa-ammâ alladhîna âmanû fa-ya'lamûna annahû al-haqq min rabbihim):"

With this phrase [the Qur'an] points out the way to prove the statement made by the previous one. It alludes too to the way to repulse ungrounded fears. That is, whoever looks with the light of belief, and from the point of view of Allâh the Most High and His power, bearing in mind His wisdom, grace, and dominicality, will know that this is [the parables are] true and [in conformity with] eloquence. But the person who looks from the depths of his soul and from the point of view of contingent beings is bound to attract delusions. This resembles two people who went up hill and down dale till they encountered a number of streams. One of them continued uphill and came to the spring. He tasted the water and found it clear and fresh. [He then descended and] whenever he came across a small piece of water from the tributaries of the streams he knew it to be good, though this was on the slightest evidence, and no delusions could mislead him however powerful. The other man, however, went downhill and sought the water from the tributaries. He did not [climb to or] see the spring and therefore needed strong evidence so as to know from the small amounts of water he encountered whether or not each bit was good. The least suspicion cast him into doubt. Or it resembles two people between whom is a mirror: one of them looks at the transparent glass, and the other at its coloured back.

In Short: When observing the art of the Most High one has to look from His point of view (min jânibihi) and noticing His grace and dominicality. This is to look with the light of belief, while delusions - even the most powerful of them - become flimsier than a spider's web. But if one looks at [divine art] from the point of view of contingent beings, with the narrow view of a customer, frail delusions will grow powerful in his sight and the truth will be hidden from him, just like a gnat's wing may prevent the eye seeing Mount Judi.