Hadith: I said: O Messenger of Allah, teach me a supplication. He said: Say O Allah, I seek refuge in You from the evil of my hearing, from the evil of my sight, from the evil of my tongue, from the evil of my heart, and from the evil of my semen

عن شكل بن حميد رضي الله عنه قال: قلت: يا رسول الله، عَلِّمْنِي دعاء، قال: (قل: اللهم إني أعوذ بك من شر سمعي، ومن شر بصري، ومن شر لساني، ومن شر قلبي، ومن شر مَنِيِّي).
[صحيح] - [رواه أبو داود والترمذي والنسائي وأحمد]

ShakI ibn Humayd (may Allah be pleased with him) reported: I said: "O Messenger of Allah, teach me a supplication." He said: "Say: O Allah, I seek refuge in You from the evil of my hearing, from the evil of my sight, from the evil of my tongue, from the evil of my heart, and from the evil of my semen (i.e. my lust)."
Sahih/Authentic. - [At-Tirmidhi]

Explanation

In this Hadīth, Shakl ibn Humayd (may Allah be pleased with him) went to the Prophet (may Allah's peace and blessings be upon him) searching for the good of this world and the Hereafter. He did not ask the Prophet (may Allah's peace and blessings be upon him) for a perishable worldly pleasure, a handful of money, or a measure of food. Rather, he went seeking supplication. He asked the Prophet (may Allah's peace and blessings be upon him) to teach him a supplication that would benefit him in his religion and his worldly affairs. That was the attitude of the Companions; seeking bounty from Allah and His good pleasure. So the Prophet (may Allah's peace and blessings be upon him) directed him to this splendid sublime supplication, saying to him: Say 'O Allah', invoking Allah using His Name that comprises all of His Most Beautiful Names. "I seek refuge in You from the evil of my hearing", meaning I seek Allah's protection from the evil of hearing, which includes the forbidden things that a person might hear, such as false testimony, heresy, slander, disparaging the religion, and all other forbidden things that reach a person's hearing. "From the evil of my sight", meaning the sin of using it to look at forbidden things, such as indecent movies and shameless scenes. "From the evil of my tongue", meaning from every forbidden speech that can be uttered, such as false testimony, insults, cursing, disparaging Islam and Muslims, speaking about others' affairs or abandoning speaking about what should concern one. "From the evil of my heart", meaning filling the heart with anything other than the remembrance of Allah, the Almighty, or devoting heart-related acts of worship to others than Allah, the Almighty, like hope, fear, awe, and exaltation, or refraining from devoting the heart-related acts of worship to the Lord, Glorified and Exalted. "From the evil of my semen", meaning from the evil of my private parts by using them to commit what Allah has forbidden, or that they lead me to the preludes of adultery, like the (forbidden) look, touch, walk to the place of sin, determination to commit sin, and things of that nature. This blessed supplication includes preservation of the senses, which are among the blessings of Allah, the Exalted, upon His creation. The Prophet (may Allah's peace and blessings be upon him) ordered him to seek refuge in Allah only from the evil of these blessings, not from these blessings themselves by saying for example: "I seek refuge in Allah from my hearing", because these are blessings by means of which one worships Allah, the Almighty. They are not evil in the absolute sense such that refuge is sought from them; rather, refuge is sought from the evil that they might produce. Their preservation is achieved by using them in what they were created for and not using them to approach any act of disobedience or spread any vice, because one is held responsible for these blessings on the Day of Judgment, as Allah, the Exalted, says: {And do not pursue that of which you have no knowledge. Indeed, the hearing, the sight and the heart - about all those (one) will be questioned.} [Sūrat al-Isrā': 36]