The laws of property is part of every ancient law, but Judaic law includes a prohibition against envy. The word "eye" here takes on a meaning where we would use "view" or "viewpoint." This is much easier to understand than the KJV "evil eye" or the NIV which inserts the terms "envious" and "generous" out of nowhere. The words of Jesus here are more comprehensible if we translated them according to how he said them rather than trying to add our own perspective to them.

Both NIV and KJV (and most other Biblical translations) phrase the last clause as a question, but the word order doesn't follow the order Jesus usually uses to ask questions, which is much like English, puts the verbs early in the clause. Here, we can actually see that order in the first two clauses, but in the last two? Not at all. They look more like regular statements. We can add an "or" before the statement as the NIV does, but this word also can be translated as "surely," which fits better here.