Rashi: When a man comes to the breach of a ruin, the fox flees via another. It does not stand in the breach to fight.

Radak: It is like foxes that enter a breach in the wall around a vineyard, and destroy the vineyard. So were your Nevi'im ? "Shu'alim Ketanim Mechablim Keramim" (Shir ha'Shirim 2:15). The breach is called Churvah (a ruin); Yisrael are called Kerem. False Nevi'im are foxes who enter via the breach to destroy the vineyard. The breach is a Mashal for people of small Emunah. The false Nevi'im beautify their words, and Ketanei Emunah are enticed and support them, so also others heed them. They destroy Hashem's vineyard.

Malbim: A Navi must fix breaches of the nation. Your Nevi'im are like foxes in ruins. The fox prefers the breach over the fence, for (a) via the breach it enters the vineyard to destroy it, and (b) It flees via the breach. If a man comes against it in this breach, it flees via the opposite breach, in its cunning. So false Nevi'im entered breaches in the nation, and their words of flattery, that their ways are good, were accepted. (c) They fled via the breaches - when they were caught in their words and lies, they attributed them to breaches of the nation ¹ .

Radak: They are your Nevi'im, and not Nevi'ei Hashem.