Ibn Abī al-Dunyā in his book Mujābī al-Du‘ā’ (Those Whose Supplications Were Answered). He said:

Abū Hāshim narrated to us: I heard Kathīr ibn Muhammad ibn Kathīr ibn Rifā‘a say:

“A man came to ‘Abd al-Malik ibn Sa‘īd ibn Abjar, who examined his abdomen and said, ‘You have an illness that cannot be cured.’

“The man asked, ‘What is it?’

“He replied, ‘An internal abscess.’

“The man then turned and said, ‘Allah, Allah, Allah is my Lord; I associate nothing with Him. O Allah, I turn to You through Your Prophet Muhammad, the Prophet of mercy—may Allah bless him and grant him peace. O Muhammad, I turn through you to your Lord and mine, that He may have mercy on me for what afflicts me.’

“He then examined the man’s abdomen and said, ‘You have recovered; you have no illness.’”

I say: It has been reported that some of the early generations used this supplication and others like it. It has also been transmitted from Ahmad ibn Hanbal, in al-Marwadhī’s manual of pilgrimage rites, that one may seek a means of approach to Allah through the Prophet—may Allah bless him and grant him peace—in supplication. Others, however, prohibited this. If those seeking such a means intend to approach Allah through faith in the Prophet, love for him, allegiance to him, and obedience to him, then there is no disagreement between the two groups. If they intend to approach Allah through his person, then this is the point of dispute. Whatever they dispute must be referred back to Allah and the Messenger.

The mere fact that a supplication achieves its intended purpose does not establish that it is permissible under Islamic law. Many people invoke celestial bodies and created beings besides Allah, and some of what they desire comes about. Some deliberately supplicate at idols, churches, and other such places, and invoke the statues in churches, and some of what they desire comes about. Others use supplications that Muslims unanimously agree are forbidden, and some of what they desire comes about. Thus, achieving a purpose by some means does not necessarily make that means permissible, even if the purpose itself is permissible.