10 Take further a manifest proof of the resurrection of the dead, witnessed month by month in the sky and its luminaries. The body of the moon vanishes completely, so that no part of it is any more seen, yet it fills again, and is restored to its former state; and for the perfect demonstration of the matter, the moon at certain revolutions of years suffering eclipse and becoming manifestly changed into blood, yet recovers its luminous body: God having provided this, that you also, the man who art formed of blood, might not refuse credence to the resurrection of the dead, but might believe concerning yourself also what you see in respect of the moon. These therefore use thou as arguments against the Greeks; for with them who receive not what is written fight thou with unwritten weapons, by reasonings only and demonstrations; for these men know not who Moses is, nor Esaias, nor the Gospels, nor Paul.
Source: Catechetical Lectures (New Advent)