How can dua’ reverse destiny? How does gratitude increase one’s grace? How does goodness increase life span? Some muslims get confused by all these. However, if we examine the laws of cause and effect, we find that Allaah created the universe on these laws that do not change. Therefore, we will find that dua’ is a cause to an effect. For example, when you are told that you are immune to bullets if you take a shield in a trench. The trench is the reason why you are not hit by the bullets.
One of the shield Allah has proffers to be a beneficial for the mankind is Dua’. Hence, saying Dua’ affects destiny comes under the heading of taking shields, so you can take more shield as you can. Dua’ serves as a shield to destiny as dining is a shield to hunger. As for the verse of Allah that says: ‘Allah eliminates what He wills or confirms, and with Him is the Mother of the Book’ Q13:39. It was commented that what Allah eliminated are what is in the Angels books, but what is in the Lahw al-Mahfouz does not change. There are fixed things that do not change nor replaced. This is the general principle in life, just the way the essence or spirit of anything is fix while the incident changes.