https://islamqa.info/en/answers/811

Narrated `Ali:
I heard the Prophet (ﷺ) saying, "In the last days (of the world) there will appear young people with foolish thoughts and ideas. They will give good talks, but they will go out of Islam as an arrow goes out of its game, their faith will not exceed their throats. So, wherever you find them, kill them, for there will be a reward for their killers on the Day of Resurrection."
حَدَّثَنَا مُحَمَّدُ بْنُ كَثِيرٍ، أَخْبَرَنَا سُفْيَانُ، حَدَّثَنَا الأَعْمَشُ، عَنْ خَيْثَمَةَ، عَنْ سُوَيْدِ بْنِ غَفَلَةَ، قَالَ عَلِيٌّ رضى الله عنه سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ ‏ "‏ يَأْتِي فِي آخِرِ الزَّمَانِ قَوْمٌ حُدَثَاءُ الأَسْنَانِ، سُفَهَاءُ الأَحْلاَمِ، يَقُولُونَ مِنْ خَيْرِ قَوْلِ الْبَرِيَّةِ، يَمْرُقُونَ مِنَ الإِسْلاَمِ كَمَا يَمْرُقُ السَّهْمُ مِنَ الرَّمِيَّةِ، لاَ يُجَاوِزُ إِيمَانُهُمْ حَنَاجِرَهُمْ، فَأَيْنَمَا لَقِيتُمُوهُمْ فَاقْتُلُوهُمْ، فَإِنَّ قَتْلَهُمْ أَجْرٌ لِمَنْ قَتَلَهُمْ يَوْمَ الْقِيَامَةِ ‏"‏‏.‏
Reference     : Sahih al-Bukhari 5057
https://sunnah.com/bukhari:5057
In-book reference     : Book 66, Hadith 82
USC-MSA web (English) reference     : Vol. 6, Book 61, Hadith 577

Sahih Al Bukhari: 9.17: Bk 87.17
https://sunnah.com/bukhari:6878
Narrated `Abdullah: Allah's Apostle said, "The blood of a Muslim who confesses that none has the right to be worshipped but Allah and that I am His Apostle, cannot be shed except in three cases: In Qisas for murder, a married person who commits illegal sexual intercourse and the one who reverts from Islam (apostate) and leaves the Muslims."

Sahih Al Bukhari: No. 6922
https://sunnah.com/bukhari:6922
Narrated `Ikrima: Some Zanadiqa (atheists) were brought to `Ali and he burnt them. The news of this event, reached Ibn `Abbas who said, "If I had been in his place, I would not have burnt them, as Allah's Apostle forbade it, saying, 'Do not punish anybody with Allah's punishment (fire).' I would have killed them according to the statement of Allah's Apostle, 'Whoever changed his Islamic religion, then kill him.'"

Sahih Al Bukhari: 9.58: Bk 88.6
https://sunnah.com/bukhari:6923
Narrated Abu Burda: Abu Musa said, "I came to the Prophet along with two men (from the tribe) of Ash`ariyin, one on my right and the other on my left, while Allah's Apostle was brushing his teeth (with a Siwak), and both men asked him for some employment. The Prophet said, 'O Abu Musa (O `Abdullah bin Qais!).' I said, 'By Him Who sent you with the Truth, these two men did not tell me what was in their hearts and I did not feel (realize) that they were seeking employment.' As if I were looking now at his Siwak being drawn to a corner under his lips, and he said, 'We never (or, we do not) appoint for our affairs anyone who seeks to be employed. But O Abu Musa! (or `Abdullah bin Qais!) Go to Yemen.'" The Prophet then sent Mu`adh bin Jabal after him and when Mu`adh reached him, he spread out a cushion for him and requested him to get down (and sit on the cushion). Behold: There was a fettered man beside Abu Muisa. Mu`adh asked, "Who is this (man)?" Abu Muisa said, "He was a Jew and became a Muslim and then reverted back to Judaism." Then Abu Muisa requested Mu`adh to sit down but Mu`adh said, "I will not sit down till he has been killed. This is the judgment of Allah and His Apostle (for such cases) and repeated it thrice. Then Abu Musa ordered that the man be killed, and he was killed. Abu Musa added, "Then we discussed the night prayers and one of us said, 'I pray and sleep, and I hope that Allah will reward me for my sleep as well as for my prayers.'"

Chapter 6: WHEN IT IS PERMISSIBLE TO TAKE THE LIFE OF A MUSLIM
Sahih Muslim Bk 16, Number 4152: Bk 28.34
https://sunnah.com/muslim:1676a
'Abdullah (b. Mas'ud) reported Allah's Messenger (may peace be upon him) as saying: It is not permissible to take the life of a Muslim who bears testimony (to the fact that there is no god but Allah, and I am the Messenger of Allah, but in one of the three cases: the married adulterer, a life for life, and the deserter of his Din (Islam), abandoning the community.

Chapter 45: EXHORTATION TO KILL THE KHWARIJ
Sahih Muslim Bk 5, Number 2328: Bk 12.199
https://sunnah.com/muslim:1066a
'Ali said: Whenever I narrate to you anything from the Messenger of Allah (may peace be upon him) believe it to be absolutely true as falling from the sky is dearer to me than that of attributing anything to him (the Holy Prophet) which he never said. When I talk to you of anything which is between me and you (there might creep some error in it) for battle is an outwitting. I heard the Messenger of Allah (may peace be upon him) as saying: There would arise at the end of the age a people who would be young in age and immature in thought, but they would talk (in such a manner) as if their words are the best among the creatures. They would recite the Qur'an, but it would not go beyond their throats, and they would pass through the religion as an arrow goes through the prey. So when you meet them, kill them, for in their killing you would get a reward with Allah on the Day of judgmelat.

Sahih Muslim Bk 5, Number 2329: Bk 12.200
https://sunnah.com/muslim:1066b
A hadith like this has been narrated through another chain of transmitters.

Sahih Muslim Bk 5, Number 2330: Bk 12.201
https://sunnah.com/muslim:1066c
This hadith has been narrated on the authority of A'mash with the same chain of transmitters, but (these words) are not there:" They pass through the religion clean as the arrow passes through the prey."