Whether Mordecai’s matters would stand - Rather, “whether Mordecai’s words would hold good” - whether, that is, his excuse, that he was a Jew, would be allowed as a valid reason for his refusal.
Related Commentaries of Esther 3:4
Esther 3:4
4 Now it came to pass, when they spake daily unto him, and he hearkened not unto them, that they told Haman, to see whether Mordecai's matters would stand: for he had told them that he was a Jew.