I heard the Messenger of Allah ﷺ say, "Whoever prays twelve rakahs of Duha, Allah will build for him a palace of gold in Paradise."
حدثنا محمد بن عبد الله بن نمير وأبو كريب قالا حدثنا يونس بن بكير حدثنا محمد بن إسحق عن موسى بن أنس عن ثمامة بن أنس
سمعت رسول الله ﷺ يقول من صلى الضحى ثنتي عشرة ركعة بنى الله له قصرا من ذهب في الجنة
Its chain is daif. Tirmidhi narrated it in the chapter on Witr, in the section on what has been said about the prayer of Duha, hadith no. 473, from Abu Kurayb with this wording, and he said, "Gharib."Ibn Ishaq explicitly stated that he heard it directly in Tirmidhi's version, but Musa bin Fulan bin Anas is unknown, as stated in Taqrib and other sources.