Sunan Ibn Majah, Volume 2, Book 5, Hadith 1382 (DarusSalam) ⓘ
It was narrated that Abu Hurairah said: “The Messenger of Allah said: ‘Whoever regularly prays two Rak’ah of Duha, his sins will be forgiven even if they are like the foam of the sea.’”
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، عَنِ النَّهَّاسِ بْنِ قَهْمٍ، عَنْ شَدَّادٍ أَبِي عَمَّارٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " مَنْ حَافَظَ عَلَى شُفْعَةِ الضُّحَى غُفِرَتْ لَهُ ذُنُوبُهُ وَإِنْ كَانَتْ مِثْلَ زَبَدِ الْبَحْرِ " .
also referenced under: Hadith 1382 (Reference) & Book 5, Hadith 1445 (In-Book)