Musnad Ahmad 655:1

Muhammad ibn Sabiq narrated to us, Isa ibn Dinar narrated to us, my father narrated to us, that he heard al-Harith ibn Abi Dirar al-Khuza’i say: I came to the Messenger of Allah (may Allah bless him and grant him peace), and he invited me to Islam, so I entered it and affirmed it. Then he invited me to Zakat, and I affirmed it. I said: "O Messenger of Allah, I will return to my people and invite them to Islam and the payment of Zakat. Whoever responds to me, I will collect his Zakat, so send a messenger to me at such-and-such a time to receive what I have collected of Zakat." When al-Harith collected the Zakat from those who responded to him, and the time arrived that the Messenger of Allah (may Allah bless him and grant him peace) intended to send [a messenger] to him, the messenger was delayed and did not come to him. Al-Harith thought that some displeasure from Allah (Mighty and Majestic is He) and His Messenger had occurred regarding him. So he called for the leaders of his people and said to them: "The Messenger of Allah (may Allah bless him and grant him peace) set a time for me to send his messenger to collect what I have of Zakat. The Messenger of Allah (may Allah bless him and grant him peace) does not break his promise, and I do not see the delay of his messenger except from some displeasure that has occurred. So let us set out and go to the Messenger of Allah (may Allah bless him and grant him peace)." The Messenger of Allah (may Allah bless him and grant him peace) had sent al-Walid ibn Uqbah to al-Harith to collect what he had of the Zakat he had gathered. When al-Walid traveled and reached part of the way, he became afraid and returned. He came to the Messenger of Allah (may Allah bless him and grant him peace) and said: "O Messenger of Allah, al-Harith withheld the Zakat from me and wanted to kill me." The Messenger of Allah (may Allah bless him and grant him peace) dispatched a military force to al-Harith. Al-Harith was approaching with his companions when he met the force that had departed from Medina. They said: "This is al-Harith." When he reached them, he said to them: "To whom were you sent?" They said: "To you." He said: "And why?" They said: "The Messenger of Allah (may Allah bless him and grant him peace) sent al-Walid ibn Uqbah to you, and he claimed that you withheld the Zakat from him and wanted to kill him." He said: "No, by the One who sent Muhammad with the truth, I did not see him at all, nor did he come to me." When al-Harith entered upon the Messenger of Allah (may Allah bless him and grant him peace), he said: "Did you withhold the Zakat and want to kill my messenger?" He said: "No, by the One who sent you with the truth, I did not see him, nor did he come to me. I only came when the messenger of the Messenger of Allah (may Allah bless him and grant him peace) was delayed, fearing that there might have been some displeasure from Allah (Mighty and Majestic is He) and His Messenger." He said: Then [the verses of] Surat al-Hujurat were revealed: "O you who have believed, if there comes to you a disobedient one with information, investigate, lest you harm a people out of ignorance and become, over what you have done, regretful" [al-Hujurat: 6], up to this point: "As bounty from Allah and favor. And Allah is Knowing and Wise" [al-Hujurat: 8].