The Messenger of Allah ﷺ said, "Ibrahim never told a lie except for three. Two were for the sake of Allah, his saying 'I am sick' [Saffat 37:89], and his saying 'Rather, this big one of them did it' [Anbiya 21:63]. The third concerned Sarah, when he said, 'She is my sister.'" And he mentioned the rest of the hadith.
أن رسول الله ﷺ قال: لم يكذب إبراهيم قط إلا ثلاث كذبات ثنتين في ذات الله قوله {إني سقيم} [الصافات: ٨٩] إني وقوله: {بل فعله كبيرهم هذا} [سورة الأنبياء: ٦٣]، وواحدة في شأن سارة: إنك أختي وذكر الحديث.
Bukhari narrated it in the Book of the Prophets (3358), and Muslim in the Book of Virtues (2371), both from the hadith of Ayub Sakhtiyani, from Muhammad bin Sirin, from Abu Hurairah, who mentioned it.