Rashi: It said "Dirshu Hashem" (55:6), and they do not listen. It returns to say, the Nevi'im scream to you and announce to repent, and it will be good for them. All the leaders are like blind people; they do not see the outcomes. They are like a lookout appointed to see the sword approaching to warn the nation, and he is blind from seeing it and mute from warning them.

Radak: After the consolation, the Navi returns to rebuke Yisrael of his generation, who were evil. Their seers, the false Nevi'im who veer them to an evil path, are blind.

Malbim: Chayos that come to tear from the flock] need not fear lest the dogs guarding it bark, for there are three qualities needed for guard dogs, and all are lacking. (a) They must see one who comes to tear at night - the dogs are blind! Also refer to 56:10:3:4, 56:10:5:3.

Radak: "Ivrim" refers to blindness of the heart.

Rashi: The lookout is like a dog appointed to guard a house, and it is mute from barking. So the leaders of Yisrael do not warn them to improve.

Radak: Dogs guard flocks. When they sense a vicious Chayah approaching, they bark, and the Chayah goes away. The false Nevi'im present themselves as lookouts and guardians of Yisrael, but they are like mute dogs that cannot bark. They do not help the flock. The Chayah comes, and tears among the flock like it desires.

Radak citing a Midrash: Is there a mute dog?! Rather, when one throws a slice to a dog, it closes its mouth; so were Yisrael's judges.

Malbim: Guard dogs must be able to bark - the dogs are mute!

Rashi citing Dunash, Targum Yonasan: They sleep lying down. There is nothing like this in Tanach.

Radak #1: The false Nevi'im are like dogs that love to sleep. They do not waken from the roaring of the Chayah; it comes and tears. It is as if the dogs do not exist; they do not help the flock. Rather, they harm it, for the shepherd relies on them to bark, lest the Chayah tear. So the false Nevi'im present themselves as guardians of Yisrael, but the Resha'im come, who are like vicious Chayos, and destroy in Yisrael. The guards harm them, and do not help them. Due to the evil path that they lead them in, the enemy comes against Yisrael.

Radak #2: Normally, dogs love to sleep. The lookouts are compared to dogs, for also they love to sleep.

Malbim: Guard dogs must stay awake the entire night - the dogs love to sleep!