Or HaChaim on Genesis 42:12/אור החיים על בראשית מ״ב:י״ב

1 ויאמר אליהם לא. He said to them: "NO!" "Your words are not convincing since your actions contradict what you have said. You have demonstrated by your actions that you were searching for weak points in the land. I know this because you have each entered the country by a different border point (compare Bereshit Rabbah 91,6). The only reason for this is that you wanted to spy.