Allah's Messenger said: "Whoever prays twelve Rak'ah of Ad-Duha, Allah will build a castle made of gold for him in Paradise."
Jami` at-Tirmidhi Book 3, Hadith 21
← Previous Hadith "I was with Ibn Umar on a journey and I fell behind him. He said: 'Where were you?' I said: 'I prayed Al-Witr.' He said: 'Is there not a good exampled for you in Allah's Messenger? I saw Allah's Messenger performing Al-Witr on his mount.'"

Jami` at-Tirmidhi Book 3, Hadith 20 Next Hadith → "No one informed that they saw Allah's Messenger praying Ad-Duha except Umm Hani. She narrated that Allah's Messenger entered her house on the Day of the Conquest of Makkah. He performed Ghusl and performed eight voluntary Rak'ah such that she had not ever seen him pray any Salat lighter than them, but that he completed the bowing and prostrations."

Jami` at-Tirmidhi Book 3, Hadith 22