A man came to the Commander of the Faithful and said, 'Verily I have supplicated to Allah, but I have not received an answer!', the Imam (AS) said, 'You have described Allah in a manner that he is not worthy of being described, for verily supplication has four stages: sincerity of the heart, making the intention, having true knowledge of the means, and being fair regarding the request. So did you supplicate knowing these four conditions?' He said, 'No', then the Imam (AS) said, 'Then know them now.'