Reference for Kiddushin 153:13

תנו רבנן איזו היא חללה כל שנולדה מן הפסולים מאי פסולים אילימא פסולים לו הרי מחזיר גרושתו דפסולה לו ובניה כשרים דכתי' (דברים כד, ד) תועבה היא היא תועבה ואין בניה תועבים

though she is unfit for him, yet her children are fit, as it is written, she is an abomination:<span class="x" onmousemove="('comment',' Deut. XXIV, 4.');">²²</span> 'she is an abomination but her children are no abomination! - Said Rab Judah This is its meaning: What is a halalah? - One who was born of a priestly disqualification.<span class="x" onmousemove="('comment',' I.e., of a person disqualified to marry a priest.');">²³</span> Only one who was born [of such a forbidden union], but not one who was not born [thus]?

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