The city of מודיעין played an interesting role in preparations for Pesach. This was considered a city of כהנים, as it was in close proximity to Jerusalem.
There was an exemption to offer the קרבן פסח if one was בדרך רחוקה, far away from the Beit Hamikdash. He was allowed to offer it on פסח שני.
However, if someone reached מודיעין by the fourteenth of Nissan in the morning, he could not use the דרך רחוקה exemption.
It was assumed that if one left Modiin on foot on the fourteenth, he would get to Jerusalem.
The Gemara in פסחים says, איזוהי דרך רחוקה? מן המודיעין ולחוץ. The exception to this rule is if one is held up by caravans blocking the road. He is allowed פסח שני if he doesn’t have a horse or camel.
Another interesting Modiin Halacha is that if one finds a stray lamb close to Pesach, and it is between Jerusalem and Modiin, it must be assumed that lamb is sanctified. Someone’s קרבן פסח ran away. This animal must be treated as הקדש. It should be offered as a קרבן.
It is doubtful if today’s Modiin is in the same location as ancient Modiin. It seems that ancient Modiin was closer to Jerusalem.
Nonetheless, this city played a significant role in Passover preparations.