Musnad Ahmad 31:145

Abu Amir narrated to us, Ali narrated to us, from Abu al-Mutawakkil, from Abu Sa’id, that the Prophet, peace and blessings of Allah be upon him, said: "There is no Muslim who supplicates with a supplication in which there is no sin and no severing of ties of kinship, except that Allah gives him one of three things: either his supplication is hastened for him, or He stores it for him in the Hereafter, or He averts from him an equivalent amount of evil." They said: "Then we will increase [in supplication]." He said: "Allah is greater [in bounty]."