Another proof is the hadith of Mu'adh ibn Jabal, when the Prophet, may Allah’s peace and blessings be upon him, sent him to Yemen near the end of his life. He said: “Inform them that Allah has made five prayers obligatory upon them each day and night” (1). He did not mention the Duha prayer; had it been obligatory, the Prophet, may Allah’s peace and blessings be upon him, would have mentioned it.
The apparent meaning of his statement, “The Duha prayer is recommended,” is that it is an unrestricted sunnah.
The evidence for this is the hadith of Abu Hurayrah (2), Abu al-Darda' (3), and Abu Dharr (4): the Prophet, may Allah’s peace and blessings be upon him, advised them to pray two rak'ahs in the Duha time. Abu Hurayrah said: “My beloved friend, may Allah’s peace and blessings be upon him, enjoined three things upon me: the two rak'ahs of Duha, that I pray Witr before I sleep, and that I fast three days of every month.”
The apparent meaning of this is that it is an unrestricted sunnah to be observed every day.
Some scholars held that it is not a sunnah, because many hadiths have been reported from the Prophet, may Allah’s peace and blessings be upon him, stating that he did not perform it (5).