“The so called Luna, half moon, or sickle of the moon, also waning and waxing moon, is a sign of fertility, related to life and death, and thus a popular symbol in many religions. It pinpoints changing seasons, ebb and tide (and related inundations as harbingers of fertility), and the feminine menstrual cycle. The half moon was the attribute of Luna and more specifically of Selene. It was later transferred to Diana (Artemis), offspring of the earth mother, and known not only as virgin but also as protectress of the newborn and symbol of fertility in her own right. Biblical references use the moon symbol to highlight cosmic events, divine epiphanies and the ephemeral nature of human life and history (see, for example, Isaiah 30,26; 60,19; Revelations 21,23). Patristic times saw in the symbol of the moon, or the mysterium lunae, i.e. the three phases of the moon: dying (waning), generating (waxing) and giving birth (full moon) a valid representation of the Church (ecclesia). Ecclesia is virginal and “dying” in the encounter with Christ, the bridegroom; she is maternal and lifegiving in her spousal relation with the redeemer, and resplendent in her grace-filled existence.
John the Baptist is sometimes connected with the waning moon (Baptisry of Östr Hoby, Sweden, 12c) to explicate his role as the last prophet of the waning Old Testament which is regarded, simultaneously, as a promise of the New Testament. The moon contrasts here the sun as symbol of fulfillment, in other words, the New Testament, more specifically Jesus Christ himself, the sol invictus. The same contrast is used to signify ecclesia and synagoga. The latter is identified with the symbol of the waning moon.”