We all know very well that we are all sinners. No matter how good we think we are, how 'religious' we look, or how good people think we are, we are ALL sinners - without exception. Sometime or the other, be it in public, in private, in the darkness of night or in the brightness of daylight, we all commit sins. It's an inherent part of human nature.
As far as our own sins are concerned, we should always try to hide them and not make them public. Of course, if we have done something which has hurt someone else or denied them their rights, then we should definitely fess up and ask them for forgiveness (such as stealing something or damaging someone's property). But if we do something which we know we shouldn't be doing (such as making out with a member of the opposite sex or looking at stuff we shouldn't be seeing), we should keep quiet about it and sincerely ask Allah for forgiveness. Allah says in the Holy Quran:
Allah loves those who turn to Him constantly (for forgiveness) and He loves those who keep themselves pure and clean. (Quran, 2:222)
If we see or hear about someone else committing a sin, we should always try to ignore it. Instead of spreading it, we should hide it and keep it a secret. It is reported that the Prophet :SAW: has said:
Whosoever covers (the sins of) a Muslim, Allah covers (his sins) on the Day of Judgment. (Reported by Bukhari)
If we find it too difficult to keep it secret, the most we are allowed to do is discuss the issue with the person, in private, and try to encourage them to stop committing the sin(s). Allah has said:
The believers, men and women, are Auliyâ' (helpers, supporters, friends, protectors) of one another, they enjoin Al-Ma'rûf (i.e. Islâmic Monotheism and all that Islâm orders one to do), and they forbid (people) from Al-Munkar (i.e. polytheism and disbelief of all kinds, and all that Islâm has forbidden). (Quran, 71:9)
The only exception to this is if we find out that someone has committed a crime that has left someone injured or killed, or in which something was stolen or someone was denied something to which they were entitled to. In these cases, we MUST make the information public so that the person is brought to justice.
One thing we must not do when we find out about someone else's sins is discuss them and gossip about them. Why? Because doing so will considered backbiting, which has been compared to eating the flesh (meat) of our own dead brother. Allah Subhanahu wa T'ala has said:
O you who believe! Avoid much suspicions, indeed some suspicions are sins. And spy not, neither backbite one another. Would one of you like to eat the flesh of his dead brother? You would hate it (so hate backbiting). And fear Allâh. Verily, Allâh is the One Who accepts repentance, Most Merciful. (Quran, 49:12)
But what if what we're saying is really true?
Allah's Apostle :SAW: said:
Do you know what is backbiting? They (the Companions) said: Allah and His Apostle (peace be upon him) know best. Thereupon he (the Prophet) said: Backbiting implies your talking about your brother in a manner which he does not like. It was said to him: What is your opinion about this that if I actually find (that weakness) in my brother which I made a mention of? He said: If (that weakness) is actually found (in him) what you assert, you in fact backbited him, and if that is not in him it is a slander. (Reported by Muslim)
If we enjoy spreading stuff about people, we must think about what we are doing. Allah says in the Holy Quran:
Those who love (to see) scandal published (and) broadcast among the Believers will have a grievous Penalty in this life and in the Hereafter: Allah knows and ye know not. (Quran, 19-24)
In the above verse, Allah is warning all those who like to spread scandals and gossip about other believing Muslims to be careful, because they "will have a grievous Penalty in this life and in the Hereafter".
May Allah protect us all, and may He forgive all our sins.
Ameen.
Update
'Abd Allah reported that the Prophet of Allah, upon him be peace, said, "A believer is not a fault-finder and is not abusive, obscene, or course."
(Hadith - Bukhari's Book of Manners 313, Ahmad, Ibn Hibban, and Hakim)
... Ibn 'Abbas said, "If you wish to mention the faults of your friend, mention your own faults first."
(Hadith - Bukhari's Book of Manners 329)
... Ibn 'Abbas said on the following verse of the Qur'an, "Nor defame one another" (49:11), "Do not spend your time finding fault with one another."
(Hadith - Bukhari's Book of Manners #330)
Jubayr ibn Nufayr reported that Mu'adh ibn Jabal said, "If you love someone, do not quarrel with him and do not annoy him. Do not ask others about him, for the one you ask might be his enemy and thus tell you things about him that are not true and thus break you apart."
(Hadith - Bukhari's Book of Manners 545)
'Amr ibn al 'As said, "...I am amazed at one who spots an impurity in the eye of another but is unable to detect it in his/her own eye, or who attempts to remove a grudge from another's heart while making no attempt to remove grduges from his/her own heart. I have never blamed anyone for the confidences of mine that they have betrayed. How could I, when already they have given me reason for pause?"
(Hadith - Bukhari's Book of Manners #889 and Ibn Hibban)
Bilal ibn Sa'd al Ash'ari reported that Mu'awiyah wrote to Abu Darda' "Write to the wrongdoers of Damascus." So he asked, "What do I have to do with the wrongdoers of Damascus? How will I know them?" Abu Darda's son, Bilal said, "I will write to them," which he did. Then Abu Darda' said [to Bilal], "How did you know to whom to write? You could not have known they were wrongdoers unless you were one of them. Begin with yourself!" So he did not address the letter in anyone's name.*
(Hadith - Bukhari's Book of Manners 1295)
·i.e. he didn't single out a specific person as a wrongdoer, but spoke about wrongdoings in general, to come as a reminder (of Quran and Sunnah) to the people.
Source: TurnToIslam