Hazrat Moulana Ashraf Ali Thaanwi (rahimahullah) once mentioned the following:
In today’s times, the condition of people is quite strange. If a person does any pious deed, then he begins to wait for ilhaam or wahi (divine inspiration or revelation), thinking to himself that perhaps he will hear a voice from the sky (informing him that his action is accepted), or if he makes dua for some worldly need to be fulfilled, then he begins to wait for a sign showing him that his dua is answered. How foolish indeed is this attitude!
Nabi Musa (‘alaihis salaam) made dua to Allah Ta‘ala against Fir’aun (that Allah Ta‘ala punish him), and Allah Ta‘ala even informed Nabi Musa (‘alaihis salaam) and Nabi Haaroon (‘alaihis salaam) that both their duas had been accepted. However, the outcome of the acceptance of this dua was only seen forty years later.
It is a sign of a person’s boldness and feeling over-confident that he makes dua, and then expects to see immediate results. This was not even experienced by the Ambiyaa (‘alaihimus salaam), even though they were such that their duas were always accepted (i.e. they did not always see the outcome of their duas materialize immediately).
(Malfoozaat Hakeemul Ummat 1/79-80)