Its minimum is two rak'ahs, and its maximum is eight ………
His statement, “Its minimum”: that is, the minimum Duha prayer is two rak'ahs, because two rak'ahs are the least that is legislated for prayers other than Witr. Thus, it is not recommended for a person to offer a voluntary prayer consisting of one rak'ah, nor is that prescribed for him except in Witr. This is why the Prophet, may Allah’s peace and blessings be upon him, said to the man who entered while he was delivering the Friday sermon: “Stand and pray two rak'ahs, and keep them brief” (1). Had anything less than two rak'ahs been prescribed, he would have instructed him to do that so that he could listen to the sermon. This is why the Prophet, may Allah’s peace and blessings be upon him, instructed him to keep the two rak'ahs brief.
Further evidence for this is the hadith of Abu Hurayrah, may Allah be pleased with him, who said: “My close friend, may Allah’s peace and blessings be upon him, enjoined upon me three things: fasting three days of every month, praying the two rak'ahs of Duha, and praying Witr before I sleep” (2).
The correct view is that a voluntary prayer of one rak'ah is invalid, although some scholars held that it is valid to offer a voluntary prayer of one rak'ah. However, this is a weak view, as mentioned previously.
His statement, “Its maximum is eight”: that is, the maximum Duha prayer is eight rak'ahs, with four sets of salutations.
The evidence for this is that the Prophet, may Allah’s peace and blessings be upon him, entered the house of Umm Hani during the Conquest, when he entered Mecca, and prayed eight rak'ahs therein (3). They said: “This …”