"St. Paul of the Cross considers the separate mysteries of the redemption (the birth of Jesus and his life, passion, death, and resurrection) as the actualization and revelation of a fundamental mystery:  the endless love of God for us...

I would like you to celebrate the holy feast of Christmas in the poor stable of your own heart, where the dear Jesus will be born in a spiritual way.  Offer this poor stable to the holy Mary, Mother of God, and to the holy Joseph, so as to adorn it with virtue so that the Divine Babe will feel well there.  Many years ago I had a beautiful card from Germany picturing a beautiful Babe sleeping peacefully upon a cross.  Oh, how much I liked that symbol! . . . Therefore you, too, during this Christmas, when you have the holy Babe in your heart, completely transformed in him by love, rest with him upon the cradle of the cross... ~Paul of the Cross' letter to Maria Angela Cencelli (8th letter on December 18, 1761 in Vol.  3 on Page 130 for Paul's Letter 1343)

For Paul, the crib and cross are, we could say, manifestations or concrete expressions of the unfathomable mystery of God’s love.  The life and death of Jesus Christ are the clearest revelation of this love." ~taken from Chapter 5 of The Mysticism of the Passion in St. Paul of the Cross by Martin Bialas, CP