Musnad Abu Ya'la al-Mawsili 149:9

Shayban ibn Farrukh narrated to us, Tayyib ibn Salman narrated to us, he said: I heard 'Amrah saying: I heard the Mother of the Believers saying: I heard the Messenger of Allah, may Allah bless him and grant him peace, saying: "Whoever prays the dawn [prayer]—or he said: the morning [prayer]—then sits in his place of prayer and does not speak nonsense regarding any worldly matter, and remembers Allah until he prays four units of Duha prayer, he will emerge from his sins like the day his mother gave birth to him, having no sin."