Reference for Megillah 50:3

מעשה תמר ויהודה נקרא ומתרגם פשיטא מהו דתימא ליחוש לכבודו דיהודה קמ"ל שבחיה הוא דאודי

The story of Tamar and Judah is both read and translated. This is obvious! What might you have thought? We should be concerned about the honor of Judah. Therefore it teaches that this is actually to his credit.

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