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 of them by way of Kathir bin Zayd, from Walid bin Rabah, from Abu Hurairah, who mentioned it. Its chain is hasan on account of Kathir bin Zayd Aslami, for there is disagreement about him, but he is hasan al-hadith, and Ibn Hajar also graded it hasan in Fath al-Bari (11/24).The hadith contains a rebuke for one who peers with his sight into the inside of a house before being given permission to do so, such that if a person were to put out his eye for doing this, no compensation would be owed for it.