וַיֹּ֣אמֶר חַ֠רְבוֹנָה אֶחָ֨ד מִן־הַסָּרִיסִ֜ים לִפְנֵ֣י הַמֶּ֗לֶךְ גַּ֣ם הִנֵּה־הָעֵ֣ץ אֲשֶׁר־עָשָׂ֪ה הָמָ֟ן לְֽמָרְדֳּכַ֞י אֲשֶׁ֧ר דִּבֶּר־ט֣וֹב עַל־הַמֶּ֗לֶךְ עֹמֵד֙ בְּבֵ֣ית הָמָ֔ן גָּבֹ֖הַּ חֲמִשִּׁ֣ים אַמָּ֑ה וַיֹּ֥אמֶר הַמֶּ֖לֶךְ תְּלֻ֥הוּ עָלָֽיו׃
왕을 모신 내시 중에 하르보나가 왕에게 아뢰되 왕을 위하여 충성된 말로 고발한 모르드개를 달고자 하여 하만이 고가 오십 규빗 되는 나무를 준비하였는데 이제 그 나무가 하만의 집에 섰나이다 왕이 가로되 하만을 그 나무에 달라 하매
Tze'enah Ure'enah
“Harbonah said” [7:9]. Harbonah said to the king: Haman made a gallows on which to hang Mordecai, the good man who protected the king from death. The gallows is standing there and it is fifty cubits high. This was Haman’s downfall that he made the gallows so high that the king could see how it was made. Here one asks a question. How did Harbonah know that the gallows was to hang Mordecai, since Haman and his friends kept it a secret? The answer is that Harbonah was the messenger to call Haman to the banquet. They were taking counsel whether to still hang Mordecai at that time. The friends counseled him not to hang Mordecai, since he had become important after the honor that was done to him with the clothes and the horse. Haman was shouting at his friends that he would immediately hang Mordecai. Harbonah heard this and that is how he could tell the king all of this.
Rashi
Moreover, there is the gallows. He “also” committed another evil, that he prepared the gallows to hang the king’s friend, who saved the king from [being] poison[ed].