Expedition of Abdullah Ibn Unais

The Expedition of Abdullah ibn Unais, also known as the Assassination of Khaled bin Sufyan was the 1st attack against the Banu Lahyan, which took place in the month of Muharam in the year 4 A.H. it was reported that Khaled bin Sufyan Al-Hathali (also known as Hudayr, the chief of the Banu Lahyan tribe), considered an attack on Madinah and that he was inciting the people on Nakhla or Uranah to fight Muslims. So Muhammad sent Abdullah ibn Unais to assassinate him. Which he did successfully. After cutting off his head at night, he brought it back to Muhammad.

Attack on the chief of Banu Lahyan
Abdullah ibn Unais found Hudayr in the company of his wife, when asked about his identity. Unais replied: "'I am an arab tribesman who has heard of you and the Army you are raising to fight Muhammad, so i have come to join your ranks'"

Sufyan bin Khalid trusted him. Then Unais asked to talk to him privately, once, while conversing, Abdullah ibn Unais walked a short distance with ibn Khalid, and when an opportunity came he struck him with his sword and killed him. After killing ibn Khalid, he cut off his head, brought that to Muhammad, Muhammad gave him his staff as a reward and said:

"This will function as a sign of recognition for you and me, on the day of resurrection Musnad Ahmad 3:496"

This assassination had the effect of silencing the Banu Lahyan, for some time. But another branch of Banu Lihyan wanted to take revenge for the killing of their leader, Sufyan ibn Khalid and where thinking of means to do so.

Biographical leiterature
This event is mentioned in Ibn Hisham's biography of Muhammad. The Muslim jurist Ibn Qayyim Al-Jawziyya also mentions the event in his biography of Muhammad, Zad al-Ma'ad. Modern secondary sources which mention this, include the award winning book, Ar-Raheeq Al-Makhtum (The Sealed Nectar)

The Muslim Jurist Tabari, also mentions the event in his biography of Muhammad: "The Messenger of God called me and said, ‘It has reached me that Khalid b. Sufyan b. Nubayh al-Hudhali is gathering a force to attack me. He is either in Nakhlah or ‘Uranah, so go to him and kill him.’" Al-Tabari vol.9 p.121

Hadith literature
The incident is also mentioned in the Sunni Hadith collection Sunan Abu Dawud: The Apostle of Allah (pbuh) send me to Khalid b. Sufyan al-Hudhali. This was towards 'Uranah and 'Arafat. He (the Prophet) said: Go and kill him. I saw him when the time of the afternoon prayer had come. I said: I am afraid if a fight takes place between me and him (Khalid b. Sufyan), that might delay the prayer. I proceeded walking towards him while I was praying making a sign. When I reached near him, he said to me: Who are you? I replied: A man from the Arabs; it came to me that you were gathering (an army) for this man (i.e. the Prophet). Hence I came to you in connection with this matter. He said: I am (engaged) in this (work). I then walked along with him for a while.; when it became convenient for me, I dominated him with my sword until he became cold (dead). [Abu Dawud, book 2 no.1244] The event is also mentioned in Musnad Ahmad 3:496.