That is why Christ said, “Act in such a way that you may find eternal life, and that you may be born of water and the spirit, so that you may enter into the Kingdom.”-- Abdu'l-Baha, Some Answered Questions.
The rewards of this life are the virtues and perfections which adorn the reality of man. For example, he was dark and becomes luminous; he was ignorant and becomes wise; he was neglectful and becomes vigilant; he was asleep and becomes awakened; he was dead and becomes living; he was blind and becomes a seer; he was deaf and becomes a hearer; he was earthly and becomes heavenly; he was material and becomes spiritual. Through these rewards he gains spiritual birth and becomes a new creature. He becomes the manifestation of the verse in the Gospel where it is said of the disciples that they “were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God” —that is to say, they were delivered from the animal characteristics and qualities which are the characteristics of human nature, and they became qualified with the divine characteristics, which are the bounty of God. This is the meaning of the second birth.