He made it six, and did not make it more or less, and made it clear that this is fasting for a lifetime, according to the words of God Almighty: Whoever does a good deed will have ten times it. Most of the scholars of God are upon this, and this has a specific limit, which is that the number of Ramadan be thirty days, and if it falls below this level, and with us, it is forced by this. The six days of fasting for a lifetime are what is reduced by breaking the fast on the days on which fasting is forbidden, which are six days: the day of breaking the fast, the day of sacrifice, and the three days of Tashreeq, and the sixteenth day of Shaban is made up for with these six days. God Almighty created the heavens and the earth and all that is between them in six days, and we were what was meant by that creation, so He appeared in these six days for our sake, as was stated in the report.

So, glory be to Him, was for us in those days, so He made fasting for these six days for us.