"And there was a terror of God" (Genesis 35:5), so that they did not pursue after the sons of Jacob to cut them off and to kill them. This was because the Holy One, blessed be He, split open the earth that was beneath them down to the depth of the earth, and a fire stood between the camp of Jacob and the camp of the Perizzite. Therefore it is said, "and they did not pursue after the sons of Jacob."
Why the Terror of God Stopped the Pursuit of Jacob's Sons
Midrash Aggadah, Genesis 35:5
ויהי חתת אלהים שלא רדפו אחרי בני יעקב. להכריתם ולהרגם, לפי שבקע הקב"ה את הארץ אשר תחתיהם עד תהום הארץ, ואש היה עומד בין מחנה יעקב ובין מחנה הפרזי, לכך נאמר ולא רדפו אחרי בני יעקב: