I have seen a custom among Ashkenazic Jews that on the day before the Brit Milah of a baby boy, a group of children will come and all say the Shema to the baby. What is the origin and reason for the custom?
In Yiddish, and in contemporary terminology, this is called a vach nacht (night of watching). According to kabbalah, the night before a baby's bris is a time of danger. Therefore, we bring children to give added protection to the uncircumcised child. Additionally, it is a custom for the father of the baby, the sandak, and according to some, the mohel to stay up all night learning Torah and saying tehillim.