Musnad Abu Ya'la al-Mawsili 140:2

Khalaf ibn Hisham al-Bazzar narrated to us, Hammad ibn Zayd narrated to us, from al-Haqal ibn Ziyad, and from Yazid al-Raqashi, from Anas ibn Malik, who said: "And from the afternoon (Asr) until the setting of the sun is more beloved to me than that I should free eight of the children of Ishmael, all of them Muslims." He means: "Because I remember Allah."