<105. Surely, We have sent down to you (O Muhammad) the Book in truth that you might judge between men by that which Allah has shown you, so be not a pleader for the treacherous.>
<106. And seek the forgiveness of Allah, certainly, Allah is Ever Oft-Forgiving, Most Merciful.>
<107. And argue not on behalf of those who deceive themselves. Verily, Allah does not like anyone who is a betrayer, sinner.>
<108. They may hide (their crimes) from men, but they cannot hide (them) from Allah; for He is with them (by His knowledge), when they plot by night in words that He does not approve. And Allah ever encompasses what they do.>
<109. Lo! You are those who have argued for them in the life of this world, but who will argue for them on the Day of Resurrection against Allah, or who will then be their defender?>

Allah says to His Messenger, Muhammad,
<Surely, We have sent down to you the Book in truth>
meaning, it truly came from Allah and its narrations and commandments are true. Allah then said,
<that you might judge between men by that which Allah has shown you,>
In the Two Sahihs, it is recorded that Zaynab bint Umm Salamah said that Umm Salamah said that the Messenger of Allah heard the voices of people disputing near his tent. He went to them and said,
«I am only human, and some of you might be more eloquent in producing his argument than his brother. Thus, I might be inclined to rule in his favor because of what I hear from him. Therefore, he whom I judge to have some of his brother's right, let him not take it, for I will be cutting a piece of the Fire for him.»
Mujahid and several others among the Salaf said that this Ayah was revealed about Tu'mah bin Ubayriq, who stole a shield that belonged to an Ansari man. Tu'mah hid the shield in the house of a Jewish man, who was called Ibn Samin, according to Ibn Jarir. When the shield was discovered with the Jew, he said that Tu'mah gave it to him, and his people, Banu Zafar, supported him. They went to the Messenger of Allah and asked him to defend their man (Tu'mah), and the Prophet was about to, as he thought they were saying the truth, but Allah revealed these Ayat condemning Tu'mah and exonerating the Jew. This is why Allah said,
<so be not a pleader for the treacherous. And seek the forgiveness of Allah, certainly, Allah is Ever Oft-Forgiving, Most Merciful. And argue not on behalf of those who deceive themselves. Verily, Allah does not like anyone who is a betrayer, sinner.>
referring to Tu'mah.
Imam Ahmad recorded that Ibn 'Abbas said that a group of people from the Ansar went on a military expedition with the Messenger of Allah. A shield was stolen from one of them and a man from the Ansar was suspected of stealing it. The thief brought the shield to the house of another man and said to him, “Keep this shield for me.” Then the owner of the shield came to the Messenger of Allah and said, “My shield was stolen and I suspect so-and-so.” So, the man who was suspected came to the Messenger of Allah and said, “My people know that I am not a thief nor was I ever suspected of being a thief.” The owner of the shield then said, “I gave up on finding my shield.” Then, Allah sent down,
<Surely, We have sent down to you the Book in truth>
until,
<for he who does it, has indeed burdened himself with falsehood and a manifest sin.>
The thief later brought the shield to another man and said, “Keep it for me.” Afterwards, the thief's guilt was discovered, and the Messenger of Allah brought him and the other man to give them their judgment. The thief said, “Since you said that, then go and divide the inheritance, and try to be just in your division. Then draw lots, and each one of you should forgive his brother thereafter (regardless of who got the best share).”
Allah's statement,
<They may hide (their crimes) from men, but they cannot hide (them) from Allah;>
chastises the hypocrites because they hide their evil works from the people so that they will not criticize them. Yet, the hypocrites disclose this evil with Allah, Who has perfect watch over their secrets and knows what is in their hearts. This is why Allah said,
<for He is with them (by His knowledge), when they plot by night in words that He does not approve. And Allah ever encompasses what they do>
threatening and warning them. Allah then said,
<Lo! You are those who have argued for them in the life of this world,>
meaning, suppose these people gain the verdict from the rulers in their favor in this life, since the rulers judge according to what is apparent to them. However, what will their condition be on the Day of Resurrection before Allah, Who knows the secret and what is even more hidden? Who will be his advocate on that Day? Verily, none will support them that Day. Hence, Allah's statement,
<or who will then be their defender?>