Four Approaches to Defining Conversion Then and Now

The Rebbe, the Rogatchover Gaon, and the Avnei Nezer on giyur: its structure, the roles of milah, tevilah, and korban, and the difference between conversion in the time of the Beit Hamikdash and today.

לקוטי שיחות, חלק כו, משפטים ג