Intimacy and communication with Allah and supplication before him is of a high value that Allah doesn’t answer his servant’s request so that he constantly insists and the way for more intimacy with Allah is paved. If the very sage Allah delays the acceptance of his servant’s prayers, for he doesn’t like his servant to be apart from him.he love his servant’s weeping and supplications.he inflicts afflictions and disasters upon his servant in order that he hears his Moaning and groaning.
Imam Reza was quoted as saying:
Allah postpones answering the prayers of a believer for the sake of enthusaistically hearing his prayers and says: "it is the voice that I'd like to hear it." And hurries in answering the prayers of the hypocrite and says: "it is a voice that i do not like to hear that."3
source : erfan.ir