The Prophet ﷺ said, "A woman is not to be married while her Amtah is still married to the same man, nor while her maternal aunt is."
أخبرنا عبيد الله بن سعيد قال حدثنا يحيى قال حدثنا هشام قال حدثنا محمد
عن النبي ﷺ قال لا تنكح المرأة على عمتها ولا على خالتها
Its isnad is sahih, and it is found in Kubra, hadith 5425, and its beginning has already been mentioned at hadith 3244. Hisham is Ibn Hassan, Muhammad is Ibn Sirin, and Yahya is Qattan.