English speakers often use the idiomatic phrase “Hey – good eye!” when referring to someone who may have “caught” a discrepancy or noticed something out of the ordinary. In Hebrew this phrase has a totally different meaning.
In Biblical times when would often describe a generous person as having “a good eye”. This idiom promoted the fact that certain people could “see” a need and help to fill that need through their generosity. On the contrary one who had an “evil eye” was stingy and did not “look out” for others since they were only preoccupied with their own livelihood.