Abu Huraira reported God’s Messenger as saying, “He who throws himself from a mountain and kills himself will be thrown down in the fire of jahannam and remain in it for ever and ever; he who sips poison and kills himself will have his poison in his hand and sip it for ever and ever in the fire of jahannam; and he who kills himself with a piece of iron will have his piece of iron in his hand and will be stabbed with it in his belly in the fire of jahannam for ever and ever.”
‘Abdallah b. ‘Amr reported God’s Messenger as saying, “If anyone kills a man who has made a covenant* he will not experience the fragrance of paradise, yet its odour can be experienced at a distance of forty years’ journey.”
Bukhari transmitted it.
* Mu'ahid. This is used of a member of protected communities, but is also used of anyone who belongs to a non-Muslim community with whom a treaty of peace has been made.
God’s Messenger sent us to some people of Juhaina, and I attacked one of them and was about to spear him when he said, “There is no god but God.” I then speared him and killed him, after which I went and told the Prophet. He said, “Did you kill him when he had testified that there is no god but God?” I replied, “Messenger of God, he did that only as a means to escape death.” He asked, “Why did you not split his heart?”*
(Bukhari and Muslim.)
*He is here rebuked for attributing motives to the man when he could not know his inner motive. Splitting the heart is a figure of speech for examining the inner motives.
In the version of Jundub b. ‘Abdallah al-Bajali God’s Messenger is reported as saying several times, “How will you deal with ‘There is no god but God’ when it comes on the day of resurrection?”