Allāh the Mighty say:
You killed them not, but Allah killed them. And you (Muhammad peace be upon him) threw not when you did throw but Allah threw, that He might test the believers by a fair trial from Him. Verily, Allah is All-Hearer, All-Knower. (Surah Al Anfāl: 17)
The Prophet (peace be upon him) went to many expeditions, however, Al Imām ibn Taymiyyah while refuting the Shi’a’s false statement "Aliy as the bravest person," he said:
“The Prophet (peace be upon him) did not kill anyone with his hand except Ubayy bn Khalaf and he neither kill anyone before him nor after him. Yet, he was braver than all of the Companions .'' (Minhāj As Sunnah An Nabawiyyah fi Kalām As Shi'ah wal Qadariyyah 8/77-78)
How It Happened
During the battle of Uhud... when they got close to the mountain, Ubayy ibn Khalaf who was on a horse of his whose name was al-‘Iwadh, caught up with the Messenger of Allāh (peace be upon him). The enemy of Allāh had claimed that he would kill the Messenger of Allāh (peace be upon him) whilst riding this horse. When he got close to him, the Messenger of Allāh (peace be upon him) took a spear from al-Hārith ibn al-Simmah and killed him with it. It hit him in his collarbone and the enemy of Allāh retreated in defeat. The mushrikīn said to him, By Allāh, there is nothing wrong with you. He said, By Allāh if what is wrong with me had happened to the family of Dhu’l-Majāz, they would all have died. He used to feed his horse in Makkah and say, I will kill Muhammad riding it. News of that reached the Messenger of Allāh (peace be upon him) and he said: “Rather I will kill him insha Allāh.” When he stabbed him, the enemy of Allāh remembered that the Prophet (peace be upon him) had said, “Rather I will kill him,” and he was certain that he would die from this wound. And he died from it in Sarif on his way back to Makkah.
The story was mentioned in Sīrah ibn Hishām 3/94, Dalāil an Nubuwah of Abu Nua'aym Al Asfahāny 2/488, Dalāil an Nubuwah lil Bayhaqy 3/211, Al Jāmi' Al Ahkām al Qur'ān 7/278 , Zād al Ma'ād fi Hādiy Khayril 'Ibād 2/134, Ar Rawdhu al Anfu fit Tafsīr Sīrah an Nabawiyyah ibn Hishām 3/270, Al Bidāyah wa An Nihāyah 4/33, Tafsīr ibn Kathīr 2/1286, Al Fusūl fi Sīrah ar Rasūl of ibn Kathīr p. 66, Tasliyah al Kadhīm 4/176, and Ghazawāt ar Rasūl pp. 120-121.
Ash-Shaykh Shu'ayb Al Arnaūt graded the story Mursal in his verification of Zād Al Ma'ād 3/178.
In the verification (3/165) of Yahyah bn Muhammad and Mas'ûd bn Kāmil under the supervision of Ash Shaykh Mustafa al 'Adawy, they added: It is the Mursal of Suday, Mujāhid, Ikrimah, and Muqsim bn Al Musayyab.
I (Abu Sahl) say, there is a strong indication in the statements of Ibn Taymiyyah (as mentioned) and Al ‘Allāmah Al Ithyiobiy in his Al Bahr (31/310-311) that shows that they consider the narration authentic. Allāh knows best.
Apart from this, the ghazawāt fought by the companions, whereby the kufār were slained as ordered by the Prophet, except in some cases where he absolved himself such as the case of Usamah bn Zayd and Khalid bn Walid.
May the peace and blessing be upon the Prophet (sallallah 'alayhi wa sallam), his household, Companions, and the entire believers.