The Tanya, as I understand it, is Chabad Chasidic philosophy.
Why is the Tanya a relevant source when we are discussing Catholic concepts of the afterlife?
The teachings of the Catholic Church should be the relevant source.
The Catechism explains the relationship of the Catholic Church to the Jewish People.
839 “Those who have not yet received the Gospel are related to the People of God in various ways.”
The relationship of the Church with the Jewish People. When she delves into her own mystery, the Church, the People of God in the New Covenant, discovers her link with the Jewish People, “the first to hear the Word of God.” The Jewish faith, unlike other non-Christian religions, is already a response to God’s revelation in the Old Covenant. To the Jews “belong the sonship, the glory, the covenants, the giving of the law, the worship, and the promises; to them belong the patriarchs, and of their race, according to the flesh, is the Christ”, “for the gifts and the call of God are irrevocable.”
That being said, as people of the New Covenant, we follow the Gospel. Our teachers are the Bishops. The Old Testament is an important part of our faith. But we study it as Catholics, not as Jews.
I think it’s wonderful to learn about Judaism. But Judaism not the faith of the Catholic Church. Ours is the New Covenant, based on the death, burial, and resurrection of our Lord Jesus Christ. And you won’t find that anywhere in Jewish teaching.