Musnad Abu Ya'la al-Mawsili 243:45

Hadaba ibn Khalid narrated to us, Hammam narrated to us, Abu Jamra al-Duba'i narrated to us, from Abu Bakr, from his father, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever prays the two cool periods (al-bardayn) will enter Paradise."