Musnad Ahmad 30:803

Yazid narrated to us, Hammam ibn Yahya informed us, from Qatadah, from Abd al-Malik, from Abu Hurairah, from the Prophet (peace and blessings of Allah be upon him), who said: "Whoever Allah gives something of this wealth without him asking for it, let him accept it, for it is only a provision that Allah, the Almighty and Majestic, has driven to him."