Rasoolullah (Sallallaahu-alayhi-wasallam) is also reported as saying: "Nothing except Duas avert Taqdeer. And nothing except virtuous deeds increase life." (commentry: This means that it is established by Allah that one will make Dua due to which one's Taqdeer will change. Similarly, at times it is decided by Allah that a person will perform some good deed such as participating in Jihaad or performing Hajj due to which he is given twenty years of additional life. This is further supported by the Hadeeth that Dua is also from Taqdeer).
Rasoolullah (Sallallaahu-alayhi-wasallam) is also reported to have said that no amount of tact and prudence can help avert Qadhaa and Qadar (decree by Allah Ta'ala). But of course, making Dua to Allah helps avert any calamity that has already come and any that is yet to come. Truly, at times a calamity is imminent and a person's Dua intercepts it. The result is that the two become locked in battle and remain so till the Day of Judgement.
It is also mentioned in the Hadeeth that nothing is more valuable to Allah than Dua.
Rasoolullah (Sallallaahu-alayhi-wasallam) is reported to have said: " A person who does not invoke Allah Ta'ala, Allah Ta'ala becomes displeased with him."
Rasoolullah (Sallallaahu-alayhi-wasallam) said: "Do not fall short of making Dua as Dua protects a person from becoming ruined."
Rasoolullah (Sallallaahu-alayhi-wasallam) also said that one who desires that Allah Ta'ala grants him Duas in difficult times, it is necessary that one makes excessive Duas in good times as well.
Rasoolullah (Sallallaahu-alayhi-wasallam) said: "Dua is the weapon of a Believer, the pillar of Deen and the Noor of the heavens and earth."
Once Rasoolullah (Sallallaahu-alayhi-wasallam) chanced upon a group of people who were struck by a certain misfortune. He remarked; "Don't these people ever pray to Allah for their safety and well-being?"
Rasoolullah (Sallallaahu-alayhi-wasallam) said that any Muslim who turns his face towards Allah, asking Him (for something), Allah certainly gives him what he has asked for: either He gives it to him immediately or he keeps it (ie. the Dua) in store for him (to compensate him at a later stage or in the hereafter).
Taken from: Al-Hisnul Hasin by Allama Muhammad Al-Jazri (RA), English Rendering by: Muhammad Rafeeq Ibne Moulana Ahmed Hathurani