It is recommended to pray Duha, the least of which is two rak`ah, the best of which is eight, and the average of which is four or six, and encouragement to do so regularly Sahih Muslim 719 a

Translation

Mu'adha asked 'A'isha (Allah be pleased with her) how many rak'ahs Allah's Messenger (ﷺ) prayed at the forenoon prayer. She replied

Four rak'ahs, but sometimes more as he pleased.

It is recommended to pray Duha, the least of which is two rak`ah, the best of which is eight, and the average of which is four or six, and encouragement to do so regularly — Sahih Muslim 719 a