Ata' bin Abi Rabah narrates: I was with Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) when a young man came to him and began asking him about letting the turban hang down (leaving a tail to the turban). Ibn Umar (may Allah be pleased with them both) said: "In sha' Allah, I will tell you about it in the light of knowledge. I was the tenth of ten men in the mosque of the Messenger of Allah (peace and blessings be upon him); Abu Bakr, Umar, Uthman, Ali, Ibn Mas'ud, Hudhayfah, Ibn Awf and Abu Sa'id al-Khudri (may Allah be pleased with them all) were present. Then a young man from the Ansar came, greeted the Messenger of Allah (peace and blessings be upon him) with salam and sat down, then asked: O Messenger of Allah! Which believer is the most excellent? He (peace and blessings be upon him) said: 'The one whose character is the best.' He asked: Then which believer is the most intelligent? He (peace and blessings be upon him) said: 'The one who remembers death the most and prepares best for it before it comes; these are the most intelligent.' Then the young man fell silent, and the Prophet (peace and blessings be upon him) turned towards him and said: 'O company of the Muhajirun! There are five traits which, if you are afflicted with them and they descend among you, and I seek refuge with Allah that you should live to see them: Indecency never appears among a people to the point that they commit it openly, except that plague and diseases spread among them that had not occurred among their forefathers. They never give short measure and weight except that they are seized with years of famine, hardship of provision and the tyranny of the ruler. They never withhold the zakah of their wealth except that the rain from the sky is withheld from them, and were it not for the animals, it would never rain on them. They never break the covenant of Allah and the covenant of His Messenger except that an enemy from outside them (from other nations) is given power over them and takes away some of what is in their possession. And as long as their rulers do not judge according to the Book of Allah, Allah places mutual fighting among them.' Then he (peace and blessings be upon him) ordered Sayyiduna Abd al-Rahman bin Awf (may Allah be pleased with him) to prepare for a military expedition on which he (peace and blessings be upon him) was to send him. In the morning Abd al-Rahman (may Allah be pleased with him) had tied a turban of black cotton cloth, so the Prophet (peace and blessings be upon him) brought him close to himself, then undid it and put a white turban on him, and let (a tail) hang down on his back about four fingers' length or so, and said: 'O Ibn Awf! Tie your turban like this, for it is more beautiful and better.' Then the Prophet (peace and blessings be upon him) ordered Bilal (may Allah be pleased with him) to give him the banner. He (peace and blessings be upon him) praised and extolled Allah and sent blessings upon the Prophet (peace and blessings be upon him), then said: 'O Ibn Awf! Take it, and all of you fight in the way of Allah, fight those who disbelieve in Allah, do not steal from the spoils of war, do not act treacherously, do not mutilate anyone and do not kill any child. This is the covenant of Allah and the way of His Prophet (peace and blessings be upon him).'" This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.