Two Hebrew idioms are found in Matthew 6:22-23

"The lamp of the body is the eye. If therefore your eye is good, your whole body will be full of light. But if your eye is bad, your whole body will be full of darkness."

The words Yeshua used are good eye and evil eye. He was repeating idioms that are found in the Hebrew Scriptures. The first idiom is found in Proverbs 22:9.
"He that has a good eye shall be blessed; for he gives his bread to the poor."

This verse is written in a type of Hebrew prose called parallelism, which helps us easily discover the meaning of the idiom. The idiom appears in the first part of the parallelism and the second part defines it.

Good eye = gives his bread to the poor. Therefore, a person with a “good eye” is “a generous person that helps the poor.”

The second idiom “evil eye” is found in Deuteronomy 15:7-9

"If there is among you a poor man of your brethren, within any of the gates in your land which Yehovah your Elohim is giving you, you shall not harden your heart nor shut your hand from your poor brother, but you shall open your hand wide to him and willingly lend him sufficient for his need, whatever he needs. Beware lest there be a wicked thought in your heart, saying, ‘The seventh year, the year of release, is at hand,’ and your eye be evil against your poor brother and you give him nothing, and he cries out to Yehovah against you, and it become sin among you.”


This verse is also written in parallelism. In this case, the meaning of the idiom appears before and after it.
Hardens heart or shuts hand from poor brother = evil eye = gives him nothing.


A person with an evil eye is “a stingy person with a harden heart or closed hand that does not help the poor.” Also, note that this is a sin.


Understanding the idiom helps us to think like Yeshua.
"The lamp of the body is the eye. If therefore you are a generous person that helps the poor, your whole body will be full of light. But if you are a stingy person with a harden heart or closed hand that does not help the poor, your whole body will be full of darkness."


Yeshua was teaching about how people respond to the needs of the poor they encounter in their normal course of life using what he knew from Torah.