Musnad Abu Ya'la al-Mawsili 150:83

Ja'far narrated to us, 'Abd al-A'la narrated to us, Muhammad ibn Ishaq narrated to us, from 'Abdullah ibn Abi Bakr, from 'Amrah, from 'Aishah: She said: The Messenger of Allah (ﷺ) said: "Indeed, the most beloved of deeds to Allah is that which is continuous, even if it is little."