God takes human birth again and again upon this earth, because there is a work to do and a road to be opened towards the future. Earth nature is full of ignorance and impurity. Every time the Divine takes a human form, it works to prepare the earth nature and carry it one more step towards the goal. Avatars destroy the old impurities and bring down the new truths.
Abdul Baha recounted how Bahai followers faced torment with ecstasy, regarding it not as sacrifice but as a profound offering of their lives.
