Allah, The Most Exalted, says:

“And when My servants ask you, (Oh Muhammad), concerning Me – indeed I am near. I respond to the invocation of the supplicant when he calls upon Me. So let them respond to Me (by obedience) and believe in Me that they may be (rightly) guided. (Qur’an-2:185)

The Noble Messenger of Allah (peace be upon him) is reported to have said:

“The duas of three people are not rejected. The fasting person’s at the time of breaking fast. A Just Ruler. The oppressed person’s – whose Dua Allah takes above the clouds and the doors of the heavens are opened for it, and Allah says ‘I will certainly help you, even if it be after some time.” (Hadith-Ahmed, Tirmidhi, Ibn Hibaan)

Note: Every dua made is granted acceptance with Allah Ta’ala in one of three forms:

1. Allah Ta’ala grants the person what is requested

2. Allah Ta’ala prevents some calamity or harm from afflicting the person in exchange of the dua.

3. The reward of the dua is stored until the Day of Judgement (when the recompense will be far greater)