Wahb bin Munabbih (may Allah have mercy on him) narrates from his brother, from Sayyiduna Mu'awiyah bin Abi Sufyan (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "A man asks me for something and I withhold it so that you may intercede and be rewarded."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16858