Prophet Muhammed (p) sent Khalid ibn Walid with few hundred companions to invite people to Islam. They were instructed to invite, preach to the tribe of Banu Jadhimah.
While being there preaching Islam, some locals started shouting and saying as the reports state that “we have left our religion! We have left our religion!” Upon hearing this Khalid killed some of them.
News of this reached the Prophet (p), he was horrified at what Khalid had done and prayed to God saying, “O Allah, do not hold me to account for Khalid’s act.”
The Prophet (p) sent sent Ali (ra) to Banu Judhayma to pay blood money to those relatives who were slain, to get compensated what Khalid had done. From the reports we gather that the Prophet (p) condemned what Khalid did, he had nothing to do with he had done. He was sent to preach the message of Islam and nothing else.
“The Prophet sent Khalid bin Al-Walid to the tribe of Jadhima and Khalid invited them to Islam but they could not express themselves by saying, “Aslamna (i.e. we have embraced Islam),” but they started saying “Saba’na! Saba’na (i.e. we have come out of one religion to another).” Khalid kept on killing (some of) them and taking (some of) them as captives and gave every one of us his Captive. When there came the day then Khalid ordered that each man (i.e. Muslim soldier) should kill his captive, I said, “By God, I will not kill my captive, and none of my companions will kill his captive.” When we reached the Prophet, we mentioned to him the whole story. On that, the Prophet raised both his hands and said twice, “O God! I am free from what Khalid has done.” (Sahih al-Bukhari volume 5, Book 59, Number 628)
Kitab al-tabaqat al-kabir – Ibn Sa’d:
“Then (occurred) the sariyyah of Khalid Ibn al-Walid against Banu Jadhimah. A branch of Banu Kinanah, residing in Lower Makkah, at the distance of a day’s (journey) towards Yalamlam in Shawwal of the eighth year from the hijrah of the Apostle of Allah, may Allah bless him. It was the day of Procyon. They (narrators) said ; When Khalid Ibn al-Walid came back after the demolition of al-‘Uzza and the Apostle of Allah, may Allah bless him, was still staying at Makkah, he sent him to Bana Jadhimah TO INVITE THEM TO EMBRACE ISLAM ; he had NOT sent him to fight. He set out with three hundred and fifty persons of the Muhajirs, al-Ansar and Banu Sulaym. Khalid reached there and asked them: What are you? … He asked: What aout these arms? They said: Hostility subsists between us and an Arab tribe. He said: Put down the arms. They put down the arms and he ordered them to be made captives. The people captured them and some of them were chained behind their shoulders. He distributed them and among his companions. When it was morning, Khalid cried: He who has a captive, should strike him with the sword. As for as Banu Sulaym were concerned, they slew their captives, and as far as the Muhajirs, and al-Ansar were concerned, they set their captives free. WHEN IT (REPORT) REACHED THE PROPHET, what Khalid had done, he said: O ALLAH! I ABSOLVE MYSELF FROM THE GUILT OF WHAT KHALID HAS DONE. He sent Ali Ibn Abi Talib, who paid blood money of those who had been slain, and compensated their losses. Then he returned to the Apostle of Allah…” 
Muhammad Husayn Haykal:
“His task accomplished, ibn al Walid proceeded to Jadhimah. There, however, the people took up arms at his approach. Khalid asked them to lay down their arms on the grounds that all people had accepted Islam.
One of the Jadhimah tribesman said to his people: “Woe to you, Banu Jadhimah! Don’t you know that this is Khalid? By God, nothing awaits you once you have laid down your arms except captivity, and once you have become captives you can expect nothing but death.” Some of his people answered: “Do you seek to have us all murdered? Don’t you know that most men have converted to Islam, that the war is over, and that security is reestablished?” Those who held this opinion continued to talk to their tribesmen until the latter surrendered their arms. Thereupon, Ibn al-Walid ordered them to be bound, and he killed some of them. When he heard of the news, the Prophet lifted his arms to heaven and prayed: ‘O GOD, I CONDEMN WHAT KHALID IBN AL-WALID HAS DONE.’ The Prophet gave funds to Ali Ibn Abu Talib and sent him to look into the affairs of this tribe, cautioning him to disregard all the customs of pre-Islam. Upon arrival, Ali paid the bllod-wit of all the victims and compensated the property owners for their damages. Before leaving, he surrended the rest of the money which the Prophet had given him to the tribe just in case there were any other losses which may have escaped notice at the time.” 
Safi-ur-Rahman Al Mubarakpuri:
“KHALID IS SENT TO BANU JUDHAYMA
Realizing the need to instill Islam in the hearts of as many people as possible, the Prophet sent Khalid bin Waleed to Banu Judhayma in the month of Shawwal to preach Islam. He was accompanied by three hundred men of the Muhajireen, Ansar and Banu Sulaym. When Banu Judhayma were invited to accept Islam, they cried, ‘Sabana! Sabana!’ We have left our religion! We have left our religion!’ Their answer reeked of deceit to Khalid, who rounded them up and killed some of them. Later he ordered every Muslim soldier to kill his captive, but Ibn Umar and his comrades refused to carry out such an unjust order.
On their return, the dissenters placed the matter before the Prophet. The Prophet, horrified at what Khalid had done, prayed with his hands raised, ‘O Allah, do not hold me to account for Khalid’s act.’
He then sent Ali to Banu Judhayma to pay blood money to the relatives of those slain and to compensate those whose property had been destroyed. The money that was left over after payment of compensation was also left with the tribe.
Khalid’s actions during the expedition earned him criticism from several of the Prophet’s Companions, and there were angry exchanges between him and Abdul Rahman bin Auf. When ths altercation was reported to the Prophet, he said:
‘Khalid, refrain from saying anything harsh to my Companions. By Allah, if Mount Uhud turned into gold and you were to spend it all in the way of Allah, even then you would not equal the morning or evening prayer of any of my Companions.’” 
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 Kitab al-tabaqat al-kabir, By Ibn Sa’d, page 182-183
 The Life of Muhammad, by Muhammad Husayn Haykal, page 443 – 444
 When The Moon Split By Safi-ur-Rahman Al-Mubarakpuri, page 258 – 259