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Ayath: "And your Lord says: Call on me; I will answer (your prayer). But those who are too arrogant to serve Me will surely find themselves in Hell in humiliation."

Ayath: "When my servants ask you concerning Me, I am indeed close (to them). I listen to the prayer of every supplicant when he calls on Me. . ."

Hadith: "Dua is (a form) of worship; your Lord said, "Call on Me; I will answer you (your prayer).

Hadith: "Verily, your Lord (Blessed is He and Almighty) is alive, generous and if His servant raises his hands towards Him, He feels reluctant not to return anything to him."

Hadith: "Any Muslim who supplicates Allah with a supplication that does not contain any sin or cutting off of family relations, Allah will give him one of three things for it:
1. Either He will speedily answer his dua
2. or He will save it for him until the Hereafter
3. or He will avert something bad from him equal to the value of his dua.
(Explanation: a dua has a certain relative value determined by Allah, so if a person says a particular dua, say 15 times in a day, then Allah protects him from something bad that is equal to the valued amount of his dua.)