Messenger of Allah (ﷺ) said, 'The person who (lies) in order to conciliate between people is not a liar, when he conveys good or says (something) good".
[Al-Bukhari and Muslim].
The narration in Muslim added: She said, "I never heard him (she meant the Prophet (ﷺ)) giving permission of lying in anything except in three (things): war, conciliating between people and the conversation of man with his wife and the conversation of a woman with her husband".
- Hadith Riyad as-Salihin 249 (islam) /td> : Introduction, Hadith 249
Allah's Messenger (ﷺ) said, "Who is willing to kill Ka`b bin Al-Ashraf who has hurt Allah and His Apostle?
Thereupon Muhammad bin Maslama got up saying, "O Allah's Messenger (ﷺ)! Would you like that I kil
him?" The Prophet (ﷺ) said, "Yes," Muhammad bin Maslama said, "Then allow me to say a (false) thin
(i.e. to deceive Ka`b). "The Prophet (ﷺ) said, "You may say it." Then Muhammad bin Maslama went t
Ka`b and said, "That man (i.e. Muhammad demands Sadaqa (i.e. Zakat) from us, and he has trouble
us, and I have come to borrow something from you." On that, Ka`b said, "By Allah, you will get tire
of him!" Muhammad bin Maslama said, "Now as we have followed him, we do not want to leave hi
unless and until we see how his end is going to be. Now we want you to lend us a camel load or tw
of food." (Some difference between narrators about a camel load or two.) Ka`b said, "Yes, (I will len
you), but you should mortgage something to me.
Muhammad bin Mas-lama and his companion said, "What do you want?" Ka`b replied, "Mortgag
your women to me." They said, "How can we mortgage our women to you and you are the mos
handsome of the 'Arabs?" Ka`b said, "Then mortgage your sons to me." They said, "How can w
mortgage our sons to you? Later they would be abused by the people's saying that so-and-so has bee
mortgaged for a camel load of food. That would cause us great disgrace, but we will mortgage ou
arms to you." Muhammad bin Maslama and his companion promised Ka`b that Muhammad woul
return to him. He came to Ka`b at night along with Ka`b's foster brother, Abu Na'ila. Ka`b invite
them to come into his fort, and then he went down to them. His wife asked him, "Where are you goin
at this time?" Ka`b replied, "None but Muhammad bin Maslama and my (foster) brother Abu Na'il
have come.
His wife said, "I hear a voice as if dropping blood is from him, Ka`b said. "They are none but m
brother Muhammad bin Maslama and my foster brother Abu Naila. A generous man should respond t
a call at night even if invited to be killed." Muhammad bin Maslama went with two men. (Som
narrators mention the men as 'Abu bin Jabr. Al Harith bin Aus and `Abbad bin Bishr). S
Muhammad bin Maslama went in together with two men, and sail to them, "When Ka`b comes, I wil
touch his hair and smell it, and when you see that I have got hold of his head, strip him. I will let yo
smell his head." Ka`b bin Al-Ashraf came down to them wrapped in his clothes, and diffusin
perfume. Muhammad bin Maslama said. " have never smelt a better scent than this. Ka`b replied. "
have got the best 'Arab women who know how to use the high class of perfume." Muhammad bi
Maslama requested Ka`b "Will you allow me to smell your head?" Ka`b said, "Yes." Muhamma
smelt it and made his companions smell it as well. Then he requested Ka`b again, "Will you let m
(smell your head)?" Ka`b said, "Yes." When Muhammad got a strong hold of him, he said (to hi
companions), "Get at him!" So they killed him and went to the Prophet (ﷺ) and informed him. (Abu Rafi`
was killed after Ka`b bin Al-Ashraf." - Hadith Al Bukhari 4037 (islam)
Book 64, Hadith 84
Vol. 5, Book 59, Hadith 369 Hadith Muslim 1801 (en en2) Who will kill Ka'b b. Ashraf? He has maligned Allah, the Exalted, and His Messenger. Muhammad b. Maslama said: Messenger of Allah, do you wish that I should kill him? He said: Yes. He said: Permit me to talk (to him in the way I deem fit). He said: Talk (as you like). So, Muhammad b. Maslama came to Ka'b and talked to him, referred to the old friendship between them and said: This man (i. e. the Holy Prophet) has made up his mind to collect charity (from us) and this has put us to a great hardship. When be heard this, Ka'b said: By God, you will be put to more trouble by him. Muhammad b. Maslama said: No doubt, now we have become his followers and we do not like to forsake him until we see what turn his affairs will take. I want that you should give me a loan. He said: What will you mortgage? He said: What do you want? He said: Pledge me your women. He said: You are the most handsome of the Arabs; should we pledge our women to you? He said: Pledge me your children. He said: The son of one of us may abuse us saying that he was pledged for two wasqs of dates, but we can pledge you (cur) weapons. He said: All right. Then Muhammad b. Maslama promised that he would come to him with Harith, Abu 'Abs b. Jabr and Abbad b. Bishr. So they came and called upon him at night. He came down to them. Sufyan says that all the narrators except 'Amr have stated that his wife said: I hear a voice which sounds like the voice of murder. He said: It is only Muhammad b. Maslama and his foster-brother, Abu Na'ila. When a gentleman is called at night even it to be pierced with a spear, he should respond to the call. Muhammad said to his companions: As he comes down, I will extend my hands towards his head and when I hold him fast, you should do your job. So when he came down and he was holding his cloak under his arm, they said to him: We sense from you a very fine smell. He said: Yes, I have with me a mistress who is the most scented of the women of Arabia. He said: Allow me to smell (the scent on your head). He said: Yes, you may smell. So he caught it and smelt. Then he said: Allow me to do so (once again). He then held his head fast and said to his companions: Do your job. And they killed him. - Hadith Muslim 1801 (islam)
Book 32, Hadith 146
Book 19, Hadith 4436 Let not believers take disbelievers as allies rather than believers. And whoever [of you] does that has nothing with Allah, except when taking precaution against them in prudence. And Allah warns you of Himself, and to Allah is the [final] destination. - Quran Ali 'Imran(The Family of Imran) 3:28 (islam) Whoever disbelieves in Allah after his belief... except for one who is forced [to renounce his religion] while his heart is secure in faith. But those who [willingly] open their breasts to disbelief, upon them is wrath from Allah, and for them is a great punishment; - Quran An-Nahl(The Bee) 16:106 (islam) That [has been commanded], and whoever honors the sacred ordinances of Allah - it is best for him in the sight of his Lord. And permitted to you are the grazing livestock, except what is recited to you. So avoid the uncleanliness of idols and avoid false statement, - Quran Al-Hajj(The Pilgrimage) 22:30 (islam) “War is
deceit.” - Hadith Ibn Majah 2833 (islam)
Book 24, Hadith 81
Vol. 4, Book 24, Hadith 2833 | 
