בָּגְדָ֣ה יְהוּדָ֔ה וְתוֹעֵבָ֛ה נֶעֶשְׂתָ֥ה בְיִשְׂרָאֵ֖ל וּבִירֽוּשָׁלִָ֑ם כִּ֣י ׀ חִלֵּ֣ל יְהוּדָ֗ה קֹ֤דֶשׁ יְהוָה֙ אֲשֶׁ֣ר אָהֵ֔ב וּבָעַ֖ל בַּת־אֵ֥ל נֵכָֽר׃
Judah hath dealt treacherously, And an abomination is committed in Israel and in Jerusalem; For Judah hath profaned the holiness of the LORD which He loveth, And hath married the daughter of a strange god.
Rashi on Malachi
for Judah has profaned himself, who was the holy one of the Lord, the first of His grain.
Rashi on Malachi
and married the daughter of a foreign god that they married gentile women in Babylon, and even the priests, as is delineated in the Book of Ezra (chap. 9 and 10). Our Sages said that Malachi is Ezra.