Atheism is called a burden. On the verse, “How can I alone bear your encumbrance and your burden?” (Deuteronomy 1:12), Rashi explains that “burden” refers to the fact that there were nonbelievers among the Jews in the wilderness.

When a person travels to a tzaddik, he casts aside this heavy burden, because traveling to a tzaddik is an act of faith, the opposite of unbelief (see Likutey Halakhot, Chalukat Shutfin 2:3, 4:5, 5:7).