Sahih Bukhari
Oneness, Uniqueness of Allah (Tawheed)
Volume: 009 / Book Number: 093 / Hadith Number: 556
Narrated Anas:
Allah's Apostle said, "Whenever anyone of you invoke Allah for something, he should be firm in his asking, and he should not say: 'If You wish, give me...' for none can compel Allah to do something against His Will."