Musnad Abu Ya'la al-Mawsili 117:118

Al-Fadl ibn al-Sabah narrated to us, Abu Ubaydah narrated to us, from Muhtasib, from Thabit, from Anas, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "That I sit with a people who remember Allah from after the dawn prayer until the sun rises is more beloved to me than that I free four from the children of Ishmael, the blood money for each man of them being twelve thousand. And that I sit with a people who remember Allah from after the afternoon prayer until the sun sets is more beloved to me than that I free four from the children of Ishmael, the blood money for each man of them being twelve thousand."