Acts 12:3

‘And when he saw that it pleased the Jews, he proceeded to seize Peter also. And those were the days of unleavened bread.'

In some way the king took on board the fact that he had pleased the Jews, possibly through the expressed approval of the Sanhedrin who informed him how delighted the people were, for he then proceeded to arrest Peter in order to please them even more. It was at the time of the feast of unleavened bread, the seven days following the day of the Passover. It may be that James, like Jesus, had been slain on the day of the Passover as ‘a false prophet' so that the people might hear and fear (Deuteronomy 17:12). But now the following celebrations were in progress and so the decision was made to keep Peter in prison until the feast was over so as to avoid an uproar at festival time (compare Mark 14:2).