The Messenger of Allah ﷺ said, "The supplication of a just ruler is never rejected."
حدثنا وكيع قال حدثنا سعدان الجهني عن سعد أبي مجاهد الطائي عن أبي مدلة
قال رسول الله ﷺ الإمام العادل لا ترد دعوته
No references are available.
Its isnad is hasan. Saadan bin Bishr Juhani is truthful, Saad Abu Mujahid Tai is not problematic, and Abu Mudallah, freedman of Ayesha, is acceptable. The hadith is found in Tirmidhi 5/578, no. 3598, where he graded it hasan, and Ibn Majah 1/557, no. 1752, both in the book of fasting.