Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos)
By the Chofetz Chaim
This book lists the Torah mitzvos that can be observed today
First Section – the Positive Commandments
47. It is a positive commandment to give a Bris Milah (circumcision) to an eight year old boy
As it states in Beresheis (Genesis) 17:12, "You shall give a Bris Milah to all boys of eight days old." And it should be performed on the eighth day specifically, as it states in Vayikra (Leviticus) 12:3, "On the eighth day, circumcise the foreskin." The Bris Milah should be performed after sunrise, but if it was done from daybreak it is acceptable. A Bris Milah is performed on Shabbos if the obligation and time are certain. Milah is a positive commandment that carries with it the punishment of Kareis (a Heavenly punishment of cutting off one's soul), as it states in Beresheis 17:14, "An uncircumcised man that does not have a Milah shall get cut off (from the root of Kareis)." The commandment is upon the father to give his son a Bris Milah, and if the father does not perform the Milah, he has transgressed a positive commandment. He does not get Kareis though because Kareis is only on the baby that did not have the Milah. If a father does not give his son a Bris Milah, the son is obligated to do it himself when he is older. When he is older, if a man does not get a Bris Milah, he transgresses a positive commandment and he deserves Kareis if he knowingly did not circumcize himself. Even if he has much Torah learning and did great deeds of kindness, if he dies without a Milah, he has no portion in the World to Come. This is a great commandment because there are thirteen covenants made over it.
This applies in all places and at all times.