Narrted Ibn `Abbas: Allah's Messenger (ﷺ) said, "You will be resurrected (and assembled) bare-footed, naked and uncircumcised." The Prophet (ﷺ) then recited the Divine Verse:-- "As We began the first creation, We shall repeat it: A promise We have undertaken. Truly we shall do it." (21.104) He added, "The first to be dressed will be Abraham. Then some of my companions will take to the right and to the left. I will say: 'My companions! 'It will be said, 'They had been renegades since you left them.' I will then say what the Pious Slave Jesus, the son of Mary said: 'And I was a witness over them while I dwelt amongst them; when You did take me up, You were the Watcher over them, and You are a Witness to all things. If You punish them, they are Your slaves, and if you forgive them, You, only You are the All-Mighty the All-Wise.' " (5.117-118) Narrated Quaggas, "Those were the apostates who renegade from Islam during the Caliphate of Abu Bakr who fought them". (Sahih al-Bukhari #3447)
Since you brought this up here's something from a Sunni site. Nothing will be put forward from a shia or any other site.
Maalik ibn Nuwayrah was known by the kunyah Abu Hanzalah; he was a poet and knight, one of the knights of Banu Yarboo’, and the Prophet (peace and blessings of Allaah be upon him) employed him to collect the zakaah of his people.
The historical reports agree to some extent that Maalik ibn Nuwayrah was killed by some of the troops of Khaalid ibn al-Waleed, and that after that Khaalid married his wife Layla bint Sinaan.
As for the reason why Maalik ibn Nuwayrah was killed, and the circumstances surrounding this incident, the reports vary, but most of the earlier historians who recorded this incident, such as al-Waaqidi, Ibn Ishaaq, Wuthaymah, Sayf ibn ‘Umar, Ibn Sa’d, Khaleefah ibn Khayyaat and others, state that Maalik ibn Nuwayrah refused to pay zakaah and withheld the zakaah camels, and he prevented his people from paying it, which led Khaalid to kill him, without paying any attention to his claim that he was Muslim and prayed regularly.
Ibn Salaam said in Tabaqaat Fuhool al-Shu’ara’ (172):
Notice this bit.
'As for the reason why Maalik ibn Nuwayrah was killed, and the circumstances surrounding this incident, the reports vary'
Circumstances surrounding this incident the REPORTS VARY.
So why did some of the Sahaabah criticize Khaalid for killing Maalik ibn Nuwayrah, as was done by ‘Umar ibn al-Khattaab and his son ‘Abd-Allaah, and Abu Qataadah al-Ansaari?
The reason for that may be found in some reports, as it seems that the attitude of Maalik ibn Nuwayrah about zakaah was ambiguous at first, and did not clearly deny that it was obligatory, and he did not pay it, so these Sahaabah were not certain about his view on the issue. But Khaalid ibn al-Waleed accused him and killed him. Because Maalik ibn Nuwayrah was outwardly a Muslim and prayed, Khaalid should not have been hasty and should have investigated his case further, and see whether Maalik ibn Nuwayrah would change his mind about zakaah. So some of the Sahaabah (may Allaah be pleased with them) denounced him for that.
It says in al-Bidaayah wa’l-Nihaayah by Ibn Katheer (may Allaah have mercy on him) (6/322):
Khaalid sent the troops to al-Battaah, calling the people to Islam, and the leaders of Banu Tameem came to him, hearing and obeying, and they paid the zakaah, except for Maalik ibn Nuwayrah. It is as if he was not certain what to do and he was holding back. The troops came to him and took him and his companions prisoner, but the soldiers disagreed about what to do with them. Abu Qataadah al-Haarith ibn Rib’i al-Ansaari bore witness that they prayed, but others said that they did not give the adhaan or pray. End quote.
Because Maalik ibn Nuwayrah was one of the leaders and nobles of his people, and his stance was not clear at the beginning, his brother Mutammim ibn Nuwayrah complained to Abu Bakr al-Siddeeq (may Allaah be pleased with him) about what Khaalid had done, and he rebuked Khaalid and said that he had erred by rushing to kill Maalik ibn Nuwayrah before referring the matter to Abu Bakr al-Siddeeq and the senior Sahaabah (may Allaah be pleased with them).
Khaleefah ibn Khayyaat (1/17) narrated:
Ali ibn Muhammad narrated to us from Abu Dhi’b from al-Zuhri from Saalim that his father said: Abu Qataadah came to Abu Bakr and told him that Maalik and his companions had been killed, and he was very upset by that. Abu Bakr wrote to Khaalid telling him to come to him. Abu Bakr said: The worst that Khaalid could have done is making the wrong decision. Abu Bakr reinstated Khaalid and paid the diyah for Maalik ibn Nuwayrah, and he returned the prisoners and the wealth. End quote.
Ibn Hajar said in al-Isaabah (5/755):
His brother Mutammim came to Abu Bakr and eulogized his brother and urged him to pay the diyah and return the prisoners, so Abu Bakr set the prisoners free. Al-Zubayr ibn Bakkaar said that Abu Bakr ordered Khaalid to divorce the wife of Maalik, and ‘Umar rebuked Khaalid sternly about the case of Maalik, but Abu Bakr pardoned him. End quote.
This is the most that can be said about the story of Khaalid ibn al-Waleed killing Maalik ibn Nuwayrah. Either he was correct in killing him for withholding zakaah and denying that it was obligatory after the death of the Prophet (peace and blessings of Allaah be upon him), or he made a mistake and Khaalid rushed to kill him when he should have examined the matter and established proof. Whatever the case, this is not a slander against Khaalid (may Allaah be pleased with him)
As you can see in the entire history you will find that the matter isn't clear. Only those who want to protect Khalid bin Waleed are going to the extent of slandering and accusing a companion of the Prophet s.a.w of apostacy. And if you accuse Malik of apostasy, going astray or what ever then you're slamming your own principle of 'SAHABA ARE MEHFOOZ'. Sahaba are not MEHFOOZ anymore after this are they?