God There is no deity except Him. To Him belong the best names. (Quran 20: 8)
The Beautiful Names of Allah – Opposite & Complimentary Names
The most excellent Names belong to God: use them to call on Him, and keep away from those who abuse them they will be revenged for what they do. (Quran 7:180)
Throughout this series, we have learned that God must be referred to in the way He refers to Himself, or in the way Prophet Muhammad refers to Him.
The name As Sittir comes from the traditions of Prophet Muhammad (peace be upon him). It does not appear in the Quran.
Verily, God the All-Mighty and Majestic is Forbearing, Modest and Concealing (Sitteer); and He loves modesty and concealment. Therefore, when any of you bathe, let him conceal himself (i.e. from the sight of people). 
Who is As-Sittir The Concealer?
As-Sittir is the one who covers and conceals. He is able to conceal the biggest of sins, faults, and shortcomings at any time He desires, for whomever He wills. The Concealer is the one who can conceal and cover the believer and shield them from disgrace, or Hellfire.
Sittir comes from the root seen-taa-raa and has two main meanings; to conceal, hide or cover and to prevent or keep away. It refers to the concept of concealing something.
Sittir is the emphasised form of the root, and indicates an intense and extreme quality, and quantity, to the concealment.
As-Sittir is the only one who can conceal over and over and also cover the believer from the disgrace of his misdeeds.
Dont Expose Sins
Prophet Muhammad said:
My entire nation is safe, except al-mujahirin (those who boast of their sins). Among them is that man who commits an (evil) act, and wakes up in the morning when God has kept his sin a secret, and says, Last night I did this and that. He goes to sleep while God has kept his sin a secret but wakes up in the morning and uncovers what God has kept a secret. 2
How Should Gods Names Affect Our Lives?
Remember, we must keep our sins secret and repent to the One who is As-Sittir, He Who conceals.
Believers should keep their sins to themselves and in addition to this, we must refrain from exposing the secret sins of others.
Nowadays, people seem eager to seek out and expose the sins and bad deeds of others. At times their motivation is merely to make themselves look good. This is not the behavior of a believer.
The traditions of Prophet Muhammad tell us that if a believer covers the faults of another believer God will cover him in this life and the next.
The Prophet Muhammad (peace be upon him) said:
He, who relieves a hardship of this world for a believer, God will relieve from him a hardship of the Day of Resurrection; he who eases the way for an indebted person, God will make it easy for him in the world and the Hereafter; and he who covers a Muslims mistakes or shortcomings, God will cover him in the world and in the Hereafter. God will help a person so long as he is helping his brother. 
Conceal faults of others
Noted Islamic scholar Sheikh ibn Uthaymeen when asked about concealing the faults of others explained as follows:
What is meant by concealment is concealing the fault, but concealment cannot be praiseworthy unless it serves an interest and does not lead to any negative consequences. For example, if an offender commits an offence, we would not conceal his deed if he is known for committing evil and mischief, but if a man is outwardly righteous, then he does something that is not permissible, in that case it is required to conceal his deed. 
Al-Baihaqi said in his work entitled Al Asma wa Sifat that:
Sitteer means He Who covers up and conceals His servants profusely and He does not scandalize them openly. He loves that His servants cover themselves up and avoid that which defames them, and God knows best.
In the past, if a true believer fell short of his responsibilities and found himself in sin or derelict in his duty, he would try to cover himself and would not disclose his behavior to others.
There are many anecdotes from our righteous predecessors that demonstrate this behavior. One example is the man who went to the mosque to pray but found that the prayer was finished, so he turned his face away and tried to prevent the people from recognizing him.
God will conceal your faults
Ibn Umar narrated that he heard Prophet Muhammad (peace be upon him) say:
A believer will be brought near to his Lord on the Day of Judgment and He will envelope him in His Mercy. He will make him confess his sins by saying, Do you remember (doing) this sin or that sin? He will reply: My Lord, I remember. Then He will say: I covered it up for you in the life of this world, and today I forgive you. Then the record of his good deeds will be handed to him. 
Why Doesn’t God Call Himself “Yahweh” In The Quran?
We are often praised for our good behavior and then realize that no one knows about our sins and mistakes. God has kept this part of our character hidden from others.
As Sittir, however, is well aware of our behavior yet He shields us from the judgment of others. He is the One who conceals our faults and He chooses to hide them from other people.
Even if we are able to present ourselves in a good light and feel the love of other people, we know that there is One who sees us for what we really are. He is As Sittir, He loves and forgives us even though we are less than perfect.
Call upon As Sittir
Beauty and wealth can make us overlook or even forget our faults and shortcomings. However, if we remember God and His name As Sittir, it can serve to protect us from vanity, arrogance, and pride.
Focusing on the qualities the name As Sittir encompasses should fill us with joy because it teaches us that God is aware of every one of our defects and yet He is ready to love us, accept our repentance and He will forgive us, despite our faults.
If we receive compliments, we should thank God for concealing our deficiencies and shortcomings. God alone knows that if the people truly understood our flaws, they would not praise us.
It is God who conceals and covers our faults and His blessings cause us look better than we really are.
He is As Sittir, the Concealer.