Sahih Al Bukhari – Book of One-fifth Of Booty To The Cause Of Allah (Khumus)

Volumn 004, Book 053, Hadith Number 410. 
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Narated By Anas RA: The Prophet PBUH said, ''Every betrayer will have a flag on the Day of Resurrection" One of the two sub-narrators said that the flag would be fixed, and the other said that it would be shown on the Day of Resurrection, so that the betrayer might be recognized by it.

be·tray   (b -tr )

tr.v. be·trayed, be·tray·ing, be·trays

1.

a. To give aid or information to an enemy of; commit treason against: betray one's country.

b. To deliver into the hands of an enemy in violation of a trust or allegiance: betrayed Christ to the Romans.

2. To be false or disloyal to: betrayed their cause; betray one's better nature.

4. To make known unintentionally: Her hollow laugh betrayed her contempt for the idea.

6. To lead astray; deceive. See Synonyms at deceive.

5. To reveal against one's desire or will.

3. To divulge in a breach of confidence: betray a secret.

Everyone of us should audit himself/herself that which flag would i belong to on the day of Judgement?