explains that he had had a disagreement with “his friend,” and he had felt anger toward this friend, but he told his friend about his feelings and that ended the negative attitude toward the friend.
But then he had a disagreement with another person who was not his friend; as a matter of fact, this person was his “foe,” his enemy. No doubt, because he and his foe were not close enough to have a heart-to-heart discussion, the speaker did not tell his enemy of his anger. Because he did not talk out his wrath with the enemy, the “wrath did grow.”