كتاب الدعوات : Hadeeth No:5935 : Anas: Allah's Apostle said, "When anyone of you appeal to Allah for something, he should ask with determination and should not say, 'O Allah, if You wish, give me.', for nobody can force Allah to do something against His Will....

كتاب النكاح : Hadeeth No:4742 : Sad bin Abi Waqqas: The Prophet prevented 'Uthman bin Mazun from that (not marrying), and had he allowed him, we would have got ourselves castrated.(1)...