It is narrated from Sayyidah Umm Hani bint Abi Talib (may Allah be pleased with her) that she came to the Messenger of Allah (peace and blessings be upon him) while he (peace and blessings be upon him) was judging between the people. He (peace and blessings be upon him) kept judging between them until the day had risen high; then he (peace and blessings be upon him) stood up and prayed eight rak'ahs of Salat al-Duha (the forenoon prayer).
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21404