The Jordan river is frequently mentioned in both the Old and New Testaments, highlighting how important it is and the symbolism of it.
In particular, events that took place at the Jordan river prefigured the sacrament of Baptism, preparing the way for the spiritual cleansing that would take place.
Crossing the Jordan river
First of all, when the people of Israel cross the Jordan river to the "Promised Land," this action points to what happens spiritually in baptism, as the Catechism points out.
Naaman and cleansing in the Jordan river
Elisha the prophet instructs the leper Naaman to wash in the Jordan river, cleansing him of his leprosy.
This event prefigures the cleansing power of the waters of baptism, which clean the soul and purifies it from every stain of sin.
Jesus' baptism in the Jordan river
With these Old Testament stories in mind, it should come as no surprise that Jesus would choose to be baptized in the Jordan river by St. John the Baptist.
God carefully prepared the way for the sacrament of baptism, inaugurating it at the Jordan river, a river that has been connected to the Promised Land and the idea of complete purification.