The Prophet ﷺ said, "Once the gaze has entered, there is no permission left to seek."
أن النبي ﷺ قال: إذا دخل البصر فلا إذن.
Reported by Abu Dawud (5173), Bukhari in Adab al-Mufrad (1082), and Bayhaqi (8/339), all from the hadith of Kathir bin Zayd, from Walid bin Rabah, from Abu Hurairah, as mentioned. Its chain is hasan because of Kathir bin Zayd Aslami, for there is disagreement about him, though his hadith is hasan. Hafiz also graded it hasan in Fath al-Bari (24/11).This hadith contains a rebuke for anyone who lets his gaze enter the interior of a house before being given permission, such that if a person were to poke out his eye in that situation, no blood money would be owed for it.