From a sermon by Saint Bonaventure (+ 1274 A. D.), Franciscan theologian and Doctor of the Church:
The mysteries are these: the blessed fecundity of the undefiled Virgin; the humility, at once sublime and singular, of the superblessed Child; the courteous devotion of Blessed Joseph; the devout credulity of the simple shepherds; the new mirth of the angelic spirits; the beginning of the happiness of the whole human race; the beginning of the radiance of the Christian religion.
Saint Bonaventure, In vigilia nativitatis Domini, sermo 6; Opera omnia, ed. Franciscans of Quaracchi (1882-1902), volume 9, page 95.