Original sentence: Although descriptions (and life-span) vary, the phoenix (Bennu bird) became popular in early Christian art, literature and Christian symbolism, as a symbol of Christ representing his believed resurrection, immortality, and life-after-death
Edited sentence: Although descriptions (and life-span) vary, the phoenix (Bennu bird) became popular in early Christian art, literature and Christian symbolism, as a symbol of Jesus of Nazareth, and further, represented the christian belief in a resurrection, immortality, and the life-after-death of Jesus of Nazareth