Be ye not as the horse, or as the mule, which have no understanding. The singular is exchanged for the plural, since the "instruction" is now intended, not for the godly man only, but for all. Israel had been always stiff-necked (Exodus 32:9; Exodus 33:3, Exodus 33:5; Exodus 34:9; Deuteronomy 9:6, Deuteronomy 9:13; Deuteronomy 10:16; 2 Chronicles 30:8; Acts 7:51), like a restive horse or mule.
David exhorts them to be so no more. The horse and mule are excusable, since they "have no understanding "—or, "no discernment"—Israel would be inexcusable, since it had the gift of reason. Whose mouth must be held in with bit and bridle; rather, whose adornings are with bit and bridle to hold them in (compare the Revised Version).
Lest they come near unto thee. This clause is obscure. It may mean, "Lest they come too near to thee," so as to do thee damage, as when a riding horse tosses his head and strikes the rider in the face, or when a chariot horse rears and falls back upon the driver; or it may mean, "Else they will not come near to thee," i.
e. until they are trapped with bit and bridle, they will refuse to come near to thee.