Musnad Ahmad 1153:232

Yahya narrated to us, from al-Taymi and Ibn Abi ‘Arubah, from Qatadah, from Zurarah, from Sa‘d ibn Hisham, from ‘Aishah, from the Prophet (peace and blessings of Allah be upon him) regarding the two rak‘ahs before the dawn prayer, he said: "They are more beloved to me than the entire world."