The Jubilee year reminds us to not accept converts indiscriminately.
Returning Lost Souls Kabbalah explains that there are 3 major reasons for reincarnation.
From Shenei Luchot HaBrit by Rabbi Isaiah Horowitz
Entreaties and Prayers Moshe's entreaty demonstrated four conditions necessary for one's prayer to be accepted Translated and annotated by Rahmiel-Hayyim Drizin from PaRDeS HaBahir
