Look a horse in its mouth

[catoidtang]

What's the meaning of "Look a horse in its mouth"?
Is it different from "Look a horse gift in its mouth"?

[allenman]

One looks in the mouth of a horse to determine its age before buying it (IIRC).

If you were given a horse and you wanted to look in its mouth first it would indicate you were not satisfied with the gift.

We say "don't look a gift-horse in the mouth" for this reason. The expression applies to anything one receives for free -- not just horses :)

Not a teacher