The number of rak'ahs in the Duha prayer

The Shaykh : Then, if one of us has extra time and a desire for more obedience and worship, the Duha prayer is prescribed as two, four, six, or eight rak'ahs. This is the maximum number of rak'ahs that is authentic from the Messenger of Allah (peace and blessings be upon him) regarding the Duha prayer. If a person also has more free time, he should not exceed eight rak'ahs; rather, he should lengthen the rak'ahs by lengthening the recitation, lengthening the bowing, lengthening the prostration, and lengthening the time between them. Instead of carrying with him two rak'ahs that take, for example, four minutes, let him make it eight minutes. If he increases it, Allah will increase his reward.