פּירוש אויף אסתר 10:3

By most of his brethren. By not by all his brethren, this teaches us that part of the Sanhedrin separated from him because he became close to the monarchy and neglected his studies.¹Maseches Megillah 16b and see Rashi there.

Of all his descendants. This refers back to “of his people,” i.e., to all the seed of his people.

“Next to the king” [10:3]. Mordecai was Ahasuerus’ vizier and was important in the Torah. He bequeathed everything good to the Jews. Ibn Ezra asks a question. Why did the righteous Mordecai and Esther not mention the name of the Holy One in the whole Megillah? The answer is that Mordecai and Esther were afraid of the Persians and Medes that they would write the names of their foreign gods in the places where the Holy One is mentioned. Therefore, they did not want to mention the name of the Holy One in the Megillah.⁴⁷Abraham ibn Ezra, Commentary on Esther, Introduction.