Musnad Abu Ya'la al-Mawsili 150:413

Ishaq ibn Abi Isra'il narrated to us, Jarir narrated to us, from Layth, from a man, from Aisha, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said regarding the saying of Allah: "And those who give what they give while their hearts are fearful that they will return to their Lord" (23:60): "They are the believers." He said: "O daughter of the Truthful (al-Siddiq), or O daughter of Abu Bakr, they are those who pray, fast, and give charity, while they fear that it will not be accepted from them."