But the men of Israel saw, etc. Seeing, however, certain unlearned and ignorant of the true remedies of humility and the salutary washing of baptism, the learned in Judea, their own teachers, being defeated in the spiritual contest by the triumph of sin, and also the not small multitude of the common people, who had been close to their teaching, driven by the adversary from their ancient seat of constancy, they themselves, perturbed by the fall of their elders, lost all works of virtue and defenses of spiritual knowledge that they had; and the sins of the Gentiles came and all studies of virtue in the unbelieving Jews were corrupted by perverse inhabitation; unclean spirits came, and the hearts devoid of the constancy of faith were occupied; or certainly the Gentiles came and made the once best studies of the Jews their own by believing. For even in former times, they had themselves made the divine words, which they had already partly abandoned, be interpreted for them; and now they have received the faith of Christ cast away by them, along with the divine Scriptures, and they possess them as if by inhabitation. Indeed, that which was said, beyond the valley, and beyond Jordan, should be explained more clearly mystically, the very site of the place being intimated to a few. There is a great valley around the Jordan, itself flat, extending in immense length, called in Hebrew Elon or Aulon, which is surrounded on both sides by succeeding and coherent mountains, beginning from Lebanon and reaching beyond it to the desert of Pharan; and notable cities are in that Aulon, that is, in the flat valley, Scythopolis, Tiberias, and the lake near it; but also Jericho, the Dead Sea, and the surrounding regions; through which, as we said, the Jordan flows in the middle, rising from the sources of Paneas and ending in the Dead Sea. Since, therefore, it is not hidden that the valley signifies the lowliness of humility, and Jordan, in which the Lord deigned to be baptized, signifies the waters of baptism, it is rightly embraced by the valley of Jordan, so that the very site of the place may admonish us to seek humbly the entrance into the saving fountain and to behave humbly after we have left it. Whoever, therefore, were not in the valley of Jordan, but beyond the valley and beyond Jordan, they flee; because those who either neglect to receive or to keep the remedy of humility and baptism, can by no means prevail against evil spirits. This can generally be understood about Jews and pagans, about heretics and bad Catholics.
Source: Commentary on Samuel