Many of the early church fathers were very concerned with Christians who might be "Judaizing" -- that is, drifting from Christian practice into Jewish practice. So, they strongly discouraged Christians from listening to Jewish sermons or celebrating Jewish holy days. At times, they went so far as banning Jews from giving sermons or requiring that synagogues not have windows on the ground floor in order to prevent the sound of Jewish prayer from escaping into public spaces. At times, discouragement took the form of excommunication of any Christians who violated these standards. And then came the inquisition, when Christians who appeared to be Judaizing were at risk of execution.