The topic of dua and its relationship to destiny (qadr) is a very important one, and one around which much confusion exists. Many people ask: If everything has already been destined to occur, then of what use is dua, as, if Allah has written what I want, I will get it without making du’a and if it is not written for me, then I will never get it no matter how much dua I make?
The response to this question lies in understanding that the outcome of anything is dependent on the performance of the efforts that are necessary to procure it. In other words, it has already been decreed, for example, that a seed will give fruit if planted, but this will not occur unless the farmer takes the appropriate efforts in irrigating the crop, maintaining it, protecting the seedling as it grows, and ensuring as much as he can that the factors are amenable for the plant to give fruit.
So even though a person believes in the Divine Decree, he must at the same time strive all he can to ensure that the desired goal occurs. So dua is the means that one uses to achieve the desired goal that one has, and this means in no way contradicts the destiny that has been written for that person.
This stance is clarified by the Prophet’s ﷺ hadith reported by Thawban, that he ﷺ said:
| Nothing increases ones life-span except good deeds, and nothing repels Divine Decree except dua. And verily, a person may be deprived of sustenance due to a sin that he does!
In other words, the performance of good deeds is a cause of increasing ones life span, so if a person puts in the necessary effort, the results will be achieved, and this is also destined. So both the means to achieve a goal, and the fulfilment of the goal itself, are already decreed.
If someone were to ask: How can dua repel Divine Decree? we would respond, The fact that you may be ill has already been decreed by Allah for you, as has the fact that you will ask Allah to cure you of this illness (i.e. both the illness and your asking to cure the illness has been decreed). In a similar manner, a person maybe deprived of his sustenance that was decreed for him, since Allah’s eternal knowledge encompassed the fact that this person would perform a sinful deed that would cause the deprivation of his sustenance. All of this, then, is from the decree of Allah, all Glory and Praise be to Him.
There are a number of ahadith that clarify this point. For example, Mu’adh ibn Jabal reported that the Prophet ﷺ said:
Caution will be of no benefit against Divine Decree, but dua benefits all things, whether they come down or not. I therefore advise you to make du’a, O servants of Allah! 
So no matter how cautious a person is, he cannot escape what is written for him, simply because Allah controls everything, and nothing escapes His Knowledge or Power. However, by turning to Allah through dua, it is possible to avert something that might have been decreed. Salman al-Farsi narrated that the Prophet (SAWS) said:
| Nothing repels Divine Decree except du’a, and nothing increases ones life-span except good deeds 
This hadith informs us in no uncertain terms that the only way that we can repel some Divine Decree is through the means of du’a. So it is possible that some unpleasant matter has been preordained for us, but only if we do not make dua to avert it from us. So if dua is made, then this matter will not occur or be fulfilled, whereas if dua is left, the misfortune will occur.
Another narration in al-Tirmidhi also supports this. The Prophet ﷺ said:
| There is no Muslim on the face of the earth that asks Allah for anything except that Allah gives it to him, or averts from him a similar evil, as long as he does not ask for something evil or for breaking the ties of kinship. 
From this narration, the benefits of dua are made clear, and its value is understood. For not only is a person rewarded for making a dua, but it is also a cause of repelling an evil that was destined for him, and in obtaining the good that he was expecting.
Ibn Hajr, commenting on the benefits of dua, said:
|And the benefit of performing dua is the attainment of reward by obeying the command (of Allah to make dua), and also by the attainment of what is asked for, for there is a possibility that the request is dependent on the dua, since Allah is the Creator of both the effort and result of the effort! 
Therefore, the proper response to the question posed at the beginning of the chapter is, in the words of Ibn al-Qayyim, as follows:
| The logical consequences of such a reasoning leads to a rejection of all efforts. It can, therefore, be said to a person who holds this view, If the satisfaction of your hunger and thirst has already been destined for you, then it will be fulfilled, whether you eat or not. On the other hand, if it has not been destined for you, it will never occur, whether you eat or not. And, if a son has been destined for you, then you will be granted one, whether you have intercourse with your wife or not. On the other hand, if a son has not been destined for you, then you will never be granted one. In this case, there is no point in you getting married…!
Now, will any sane person agree with all of these conclusions? 
To summarise, then, Divine Decree ( qadr) cannot be used as an excuse not to make dua. For, just as one strives to ensure that one attains worldly needs, of food, drink and family, so too must one strive in ones religious deeds to attain the desired goal. Dua is intrinsically related to qadr; in fact, it is a part of ones qadr. Allah has already decreed that a certain matter will be granted to a servant, or an evil averted from him, if he makes dua, so if he were to leave dua, then the desired goal would not be reached.
Hence why it was the Sunnah of the Prophet ﷺ to make the following dua during the witr prayer:
| …Bless me in what You have given me. And avert and turn away from me the evil that has been decreed for me, for verily You Decree (all things), and none can decree against You…” 
So the Muslim turns to Allah and prays to Him so that any and all evil can be averted from him.
Additionally, it should be remembered that the concept of Divine Decree is one that a human can never fully understand, due to his limited intellect and finite capabilities. The true Muslim does not delve too deeply into the philosophical ramifications of Divine Decree. Rather, he accepts all that has occurred to him in the past as having been destined for him, and he strives to obtain what he desires in the future (as long as it is permissible for him). Since he does not know what has been written for him in the future, he expects the best from Allah, and does everything in his power to ensure that what he wants is granted him. Just like going to work every day will ensure, if Allah wills, that he gets his pay-cheque at the end of the month, so too does making dua ensure, if Allah wills, that he achieves his desired goal.
1 Narrated by Ibn Majah #90, and Shaykh al-Albani said in Sahih Ibn Majah (73): It is authentic without the addition, And verily…; see al-Sahihah, # 154.
2 This hadith is weak. It was narrated by Ahmad, Abu Ya’la , and al-Tabarani in al-Kabir, as has been mentioned in Daif al-Jami # 4785.
3 Authentic, reported by al-Tirmidhi and al-Hakim from Salman, and is in Sahih al-Jami # 7687.
4 Authentic, narrated by al-Tirmidhi from Ubadah ibn Samit, as is mentioned in Sahih al-Jami # 5637.
5 Fath al-Bari, 11/95.
6 Al-Jawab al-Kafi, Ibn aI-Qayyim, p. 13.
7 Reported by al-Tirmidhi (# 464), al-Nasai (# 1725) and others, with an authentic chain.