The believer is not a slanderer, nor a curser, nor obscene, nor foul-mouthed

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "The believer is not one who taunts, nor one who curses, nor one who is obscene, nor one who is vulgar."
This hadith is sahih on the condition of the two Shaykhs; they used all of these narrators as evidence, yet they did not narrate it. The most that can be said about it is that it is not found with the (general) students of al-A'mash, whereas Isra'il bin Yunus al-Sabi'i is the senior-most and leader of his students, and he shares many of al-A'mash's teachers with him, so his being alone (in narrating) this hadith is not grounds for rejecting it. This hadith also has another corroborating narration (shahid) on the condition of both of them.

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The believer is neither one who taunts, nor one who curses, nor one who is obscene, nor one who speaks vulgarly."
This hadith also has a second corroborating narration (shahid) from Ibrahim al-Nakha'i, which must be mentioned even though its chain is not on the condition of the two Shaykhs.

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "The believer is not one who taunts, nor one who is obscene, nor one who is vulgar."
Although Muhammad bin Abd al-Rahman bin Abi Layla is attributed with a poor memory, he is one of the jurists and judges of Islam, and among the eminent descendants of the Companions and Successors of the Ansar. May Allah Almighty have mercy on them.

It is narrated from Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever commits an evil deed and dislikes it while doing it, and does a good deed and is pleased by it, is a believer."
Both of them (Imam Bukhari and Muslim) used all the narrators of this hadith as evidence, and it is sahih on their condition, but they did not record it. They only narrated these words in the sermon of Sayyiduna Umar bin al-Khattab (may Allah be pleased with him): "Whoever is pleased by his good deed and saddened by his evil deed is a believer." There is also a corroborating narration (shahid) for it with these words.

It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that a man asked the Messenger of Allah (peace and blessings be upon him): O Messenger of Allah, what is faith? He (peace and blessings be upon him) said: "When your good deed pleases you and your evil deed saddens you, then you are a believer." He asked: O Messenger of Allah, what is sin? He (peace and blessings be upon him) said: "When something troubles (causes doubt in) your chest, leave it."
Ali bin al-Mubarak and Ma'mar bin Rashid likewise narrated it from Yahya bin Abi Kathir. As for the hadith of Ali bin al-Mubarak:

Sayyiduna Abu Umamah (may Allah be pleased with him) says that a man asked the Messenger of Allah (peace and blessings be upon him): What is faith? He (peace and blessings be upon him) said: "When your good deed pleases you and your evil deed saddens you, then you are certainly a believer."

It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was asked: What is faith? He (peace and blessings be upon him) said: "Whoever is pleased by his good deed and saddened by his evil deed is a believer."
All of these hadiths are sahih and connected (muttasil) on the condition of the two Shaykhs.

It is narrated from Sayyiduna Awf bin Malik al-Ashja'i (may Allah be pleased with him); he said: We halted at a stopping place with the Messenger of Allah (peace and blessings be upon him). I woke up during the night and could see nothing in the camp taller than the back of my saddle; every person and camel was clinging to the ground (asleep). I made my way between the people until I reached the bed of the Messenger of Allah (peace and blessings be upon him), but he (peace and blessings be upon him) was not there. I put my hand on the bed and it was cold. I went out between the people saying: Inna lillahi wa inna ilayhi raji'un (We belong to Allah and to Him we return), the Messenger of Allah (peace and blessings be upon him) has been taken away somewhere! until I went out beyond the whole camp. I saw a dark shape, so I threw a stone and went towards it, and there were Sayyiduna Mu'adh bin Jabal and Sayyiduna Abu Ubaydah bin al-Jarrah (may Allah be pleased with them both). In front of us there was a sound like the whirring of a mill, or like the rustling of reeds when the wind blows on them. We said to one another: O people, stay firmly here until morning comes or the Messenger of Allah (peace and blessings be upon him) comes. The narrator says: We stayed as long as Allah willed; then he (peace and blessings be upon him) called out: "Are Mu'adh bin Jabal, Abu Ubaydah bin al-Jarrah and Awf bin Malik there?" We said: Yes. So he (peace and blessings be upon him) came towards us, and we walked along with him (peace and blessings be upon him); we did not ask him (peace and blessings be upon him) anything, nor did he (peace and blessings be upon him) tell us anything, until he (peace and blessings be upon him) sat on his bed and said: "Do you know what my Lord gave me a choice between tonight?" We said: Allah and His Messenger know best. He (peace and blessings be upon him) said: "My Lord gave me a choice between having half of my Ummah admitted into Paradise, or being granted the station of intercession, and I chose intercession." We said: O Messenger of Allah, pray to Allah to make us among those who receive intercession. He (peace and blessings be upon him) said: "It is for every Muslim."
This hadith is sahih on the condition of Imam Muslim, but both of them did not narrate it. All of its narrators are trustworthy on the condition of the two Shaykhs, there is no hidden defect ('illah) in it, and the other narrations about intercession do not contain the words that it is for every Muslim.