Musnad Abu Ya'la al-Mawsili 42:46

Abu Sa’id al-Khudri said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no Muslim who calls upon Allah, Blessed and Exalted is He, with a supplication, except that He answers him, as long as there is no sin in it or severing of ties of kinship, except that Allah gives him one of three qualities for it: either He hastens his supplication for him, or He stores it for him in the Hereafter, or He averts from him an equivalent amount of evil." They said: "O Messenger of Allah, then we will increase [our supplications]." He said: "Allah is more [abundant]."