Hadith 2743
Sayyiduna Ibn Abbas (may Allah be pleased with them) said: The Noble Prophet (peace and blessings be upon him) said: "Whoever eavesdrops on people who do not like him to listen, molten lead will be poured into his ears on the Day of Resurrection."
Hadith 2744
Sayyiduna Ali (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Do not follow a glance with another glance (i.e., if your gaze unintentionally falls upon a non-mahram woman, do not look at her again), for the first glance is forgiven, but the second is a sin upon you."