This week we have a double Parsha of תזריע-מצורע. There is a Pasuk that seems redundant regarding Brit Mila. After discussing a woman who has given birth to a male, the Torah says that on the eighth day he should be circumcised. We already know about this from Avraham Avinu.
Here the Torah is teaching that Brit Mila is done even if the eighth day is Shabbat. However, a baby born by Caesarian is not circumcised on Shabbat when it is the eighth day.
It is also interesting that a baby born during twilight time, or בין השמשות on Friday evening is not circumcised until Sunday. If that day was a Chag, then not until Monday. And if it was a two day Chag outside of Israel, then not until Tuesday, the eleventh day from birth.
This is why the Mishna says that a Brit can be on the eighth, ninth, tenth, or eleventh day.
Yesterday was fifteen with ספירת העומר. Chodesh Tov