All perfect praise be to Allah the Lord of The Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Dua is an act of worship and a believer may invoke Allah for any matter of this life and the next. Allah says {What means}: "And when My slaves ask you (O Muhammad PBUH) concerning Me, then (answer them), I am indeed near (to them). I respond to the invocations of the supplicant when he calls on Me” [Surah al-Baqarah 2:186]. In another Verse, Allah says:“And your Lord said: ‘Invoke Me , I will respond to your (invocation). Verily, those who scorn My worship [i.e. do not invoke Me, and do not believe in My Oneness] they will surely enter Hell in humiliation!’”[Surah Ghaafir 40:60].
Prophet Mohammad (Peace be upon him) taught us the etiquette of making Dua to Allah and that we should invoke Him with humble submissiveness. He (Peace be upon him) also taught us to put our trust in Allah where he (Peace be upon him) said: “Nothing can change the Divine decree except dua” {Related by Tirmithi}.
This Hadith indicates that Dua is among the doors of goodness and worship. However, it doesn`t mean that what Allah had decreed can be changed. Rather, it means that the Duas made by people, their needs, and conditions are destined by Allah. This Hadith calls on Muslims not to give up on worship and Dua, as they are keys to goodness in this life and the next. Thus, a person should humbly ask Allah to grant him a pious wife and be sincere in his Dua. He should commit all his affairs to Allah the Almighty although his fate is inescapable.
This is indicated in the words of Allah Who said {What means}: " God doth blot out or confirm what He pleaseth: with Him is the Mother of the Book." {Ar-Rad, 39}. Moreover, a Muslim has no knowledge of the unseen nor knows what Allah had decreed for him/her. Therefore, he/she should make Dua as an act of worship and in compliance with the command of Allah. For more details, kindly check the book entitled {Mashkal Al-Hadith Wa Bayanoh, V.1:312}.
A believer makes Dua and seeks treatment in compliance with Allah`s command and he/she is rewarded for that. As for the results, they are in the Hands of Allah the Almighty. Every sane believer feels the impact of Dua just as he/she feels the impact of medication. Not only this, but also the truthful believers use Dua for matters that material means fail to achieve; that is the Grace of Allah which He bestows on whom He pleases. And Allah the Almighty knows best.