By the Noble Scholar, Shaykh Muhammad Ibn Saalih al-’Uthaymeen 
Majmoo’ul-Fataawaa war-Rasaa‘il (no. 155)
[Q]: ‘Allaah says: ‘‘And your Lord says: Call upon Me and I will, respond to your supplication.’’ [Soorah Ghaafir 40:60] So why is it that a person’s du’aa (supplication) is sometimes unanswered?’
[A]: ‘‘All praise is due to Allaah, Lord of the worlds. May the Prayers and Peace be upon our Prophet Muhammad, and upon his Family and his Companions. I ask Allaah for the ability to be correct in belief, speech and actions, for myself and for my brothers.
‘‘And your Lord says: Call upon Me and I will respond to your supplication. Verily those who are too arrogant to worship Me will, enter Hell in humiliation.’’ [Soorah Ghaafir 40:60]
The questioner stated that he did indeed make du’aa (supplication) to Allaah – the Mighty and Majestic – but it was not answered by Allaah. So he is in doubt with respect to this noble aayah (verse), in which Allaah promises to answer the one who supplicates to Him, and indeed Allaah – the Most Perfect – never breaks His promise.
So the clarification of this is that there are certain conditions that need to be fulfilled in order for a supplication to be answered. These conditions are:
Firstly: Sincerity to Allaah – the Mighty and Majestic. That is to say, one must be sincere in his du’aa (supplication), so he turns to Allaah – the One free from all imperfections with an attentive heart, being truthful in his turning to Him, knowing that Allaah – the Most Perfect, the Most High – is capable of answering his du’aa (supplication) and hoping that the du’aa will be answered.
Secondly: During du’aa, the caller should feel that he is in need of Allaah – the Most Perfect, the Most High – in fact in dire need; and that only Allaah alone answers the supplication of the one in distress and the One who removes evil.
Thirdly: That the one making du’aa should refrain from haraam (unlawful) matters, as this acts as a barrier between the person and his du’aa (supplication) being answered – as has been established in the authentic hadeeth, from the Prophet (sallallaahu ’alayhi wa sallam) who said: ‘‘Indeed Allaah – the Most High -is good and accepts only that which is good. Allaah has ordered the Believers to do that which He commanded the Messengers. Allaah – the Most High -has said:
‘‘O you Messengers! Eat of the good things and do righteous actions.’’ [Sooratul-Mu‘minoon 3:51 ]
And Allaah – the Most High – says:
‘‘O you who Believe! Eat of the good things wherewith We have provided you. ’’ [Sooratul-Baqarah 2:172]
Then he mentioned (the case of) a man who, having journeyed far is dishevelled and dusty and who spreads out his hands to the sky (saying): ‘O Lord! O Lord,’ whilst his food is unlawful, his drink unlawful and he is nourished unlawfully. So how can he be answered!’  So the Prophet (sallallaahu ’alayhi wa sallam) explained the un-likelihood that this person’s du’aa would be answered, even after fulfilling the apparent factors which aid the du’aa being answered. The apparent factors being:
[i]: Raising ones’ hands towards the sky, meaning towards Allaah – the Mighty and Majestic – since Allaah is above the heavens, above His ’Arsh (Throne). Extending the hands out towards Allaah -the Mighty and Majestic – is amongst the causes of du’aa being responded to, as is shown in the narration from the Prophet (sallallaahu ’alayhi wa sallam) that he said: ‘‘Indeed your Lord is Alive, Most generous. He feels shy that when his servant raises his hands towards Him, calling upon Him, that He should return him empty, having nothing.’’
[ii]: This man called upon Allaah – the Most High – using the name Rabb (Lord). Seeking tawassul (the means of nearness to Allaah) with this name is also regarded as one of the causes for du’aa to be responded to, since the Rabb is the Creator, the Owner, the Governor of all affairs – and the reigns of the Heavens and the earth are in His Hands. Due to this, you will find that most of the supplications made in the Noble Qur‘aan are by this name:
‘‘Our Lord! We have heard the call of one calling us to faith: ‘Believe you in the Lord,’ and we have believed. Our Lord! Forgive us our sins, and remit from us our evil deeds, and take to Yourself our souls in the company of the righteous. Our Lord! Grant us what You did promise unto us through Your Messengers, and do not disgrace us on the Day of judgement, for You never break Your promise. And their Lord has accepted of them, and answered them: Never will I suffer to be lost the work of any of you, whether male or female.’’ [Soorah Aal-‘lmraan 3:193-195]
So tawassul (seeking the means of nearness to Allaah) by this name is one of the causes for the du’aa to be responded to.
[iii]: This man was a traveller, and journeying is often a cause for du’aa to be responded to, because a person feels more in need of Allaah – the Mighty and Majestic – when travelling, than when a person is resident with his family. He was dusty and dishevelled, seeming very insignificant in himself, as if the most important thing to him was to implore Allaah and to call upon Him – in any condition he may be – whether dusty and dishevelled, or in ease and oppulance. Being dusty and dishevelled is also instrumental, like in the hadeeth attributed to the Prophet (sallallaahu ’alayhi wa sallam) in which he said: Indeed Allaah boasts to the people of the Heaven about the people standing at ’Arafah, saying: ‘‘Look at My servants who have come to Me dusty and dishevelled.’’  However, these factors did not bring about anything, because his food, his nourishment and his clothing were all haraam (unlawful). So the Prophet (sallallaahu ’alayhi wa sallam) remarked: ‘‘So how can he be answered!’’
Therefore, if these conditions are not satisfied, then the question concerning the du’aa (supplication) being answered will seem distant. However, if the conditions are satisfied and the one supplicating is still not answered, then this is due to a wisdom which Allaah – the Mighty and Majestic – knows, and the one supplicating does not know what this wisdom is; and maybe that you like a thing and it is bad for you.
So when these conditions are fulfilled and the one supplicating is not answered, then either he has been protected from an evil which is greater than what he has asked for, or Allaah stores it for him until the Day of Resurrection, and he then gets a greater reward. This is so, because the one who makes du’aa – calling upon Allaah alone, fulfilling the conditions and not being answered, but rather being saved from a greater evil – is in the position of having carried out the causes yet has been prevented from being answered, and therefore has a two-fold reward. One reward for making du’aa (supplication), and another reward for bearing the trial of not being answered. So that which is greater and more complete is stored for him with Allaah – the Mighty and Majestic.
Also of importance is that the one supplicating should not express dissatisfaction if his du’aa is apparently not being answered, for this action in itself is a reason for the du’aa not being answered – as the Prophet (sallallaahu ’alayhi wa sallam) said: ‘‘A servants du’aa continues to be answered as long as he does not ask for anything sinful or breaking the ties of relations, and as long as he does not become impatient.’’ It was said: How does one become impatient O Messenger of Allaah? He said: ‘‘He says: I have supplicated, I have supplicated, yet it has not been answered.’’  He therefore becomes dispondant and abandons supplicating. So it is not befitting that the one supplicating should become impatient about being answered, then become disappointed and dispondant, and thereby abandon making du’aa. Rather, one should call upon Allaah, since every du’aa you make to Allaah is an act of worship, which brings you closer to Him and increases your reward.
So my brother, you should take to making du’aa (supplication) in all affairs, be it general or specific, in difficulty or in ease. And if it was that supplication was only a means of worshipping Allaah – the One free from all imperfections, the Most High – then that would be sufficient. So it is more befitting that a person strives in this – and with Allaah lies the success and the ability.’’
 Majmoo’ul-Fataawaa war-Rasaa‘il (no. 155)
 Related by Muslim (no. 1015) from Aboo Hurayrah (radiyallaahu ’anhu)
 Saheeh: Related by Ahmad (5/438) and Aboo Daawood (no. 1488). It was authenticated by al-Haafidh Ibn Hajar in Fathul-Baaree (11/143).
 Saheeh: Related by Ibn Hibbaan (no. 1006), from ’Abdullaah Ibn ’Amr (radiyallaahu ’anhu). It was authenticated by Shaykh al-Albaanee in Saheehul-Jaami’ (no. 1868).
 Related by al-Bukhaaree (11/140) and Muslim (no. 2735), from Aboo Hurayrah (radiyallaahu ’anhu)