Neglecting Congregational Prayer
"Whoever hears the call to prayer but does not hearken to it, then he has no prayer." [Sunan al-Tirmidhî (217)]
`Alî b. Abî Tâlib said: "There is no prayer for the neighbor of the mosque except in the mosque." [Musannaf `Abd al-Razzâq (1915) and Musannaf Ibn Abî Shaybah (3469)]
"The covenant between us and them is prayer. Whoever abandons it has disbelieved." [Sunan al-Tirmidhî (2621)]
The Prophet (peace be upon him) said: "Whoever abandons the `Asr prayer, his deeds are lost." [Sahîh al-Bukharî (528)]
Backbiting & Rumor-Mongering
Prophet (peace be upon him) defined backbiting in the following way:
He said: “Do you know what backbiting is?”
They said: “Allah and His Messenger know best.”
He said: “It is to mention about your brother something that he would dislike having mentioned about him.” [Sahîh Muslim (2589)]
Someone enquired: “O Messenger of Allah! How do you see it if what I said about him is true?”
He replied: “If what you said about him is true, then you have backbitten him. If what you said about him is false, then you have slandered him.” [Sahîh Muslim (2589)]
Hudhayfah heard about a man who was spreading rumors and he said: "I heard Allah-s Messenger say: 'A rumor-monger will not enter Paradise." [Sahîh al-Bukhârî (6056) and Sahîh Muslim (105)]
Vulgar Speech and Bad Manners
Abû Hurayrah relates that the prophet (peace be upon him) said: "Whoever does not abandon false speech and acting falsely, then Allah has no need of his abandoning food and drink." [Sahîh al-Bukhârî (1903)]
The Prophet (peace be upon him) said: "Fasting is a shield, so the one who fasts should avoid obscene speech and ignorant behavior. If someone abuses him or starts to fight with him, he should reply by saying: 'I am fasting.'" [Sahîh al-Bukhârî (1795)]
Excessive Eating and Drinking
It is related from al-Miqdâm b. Ma`di Yakrib that the Prophet (peace be upon him) said: "The human being does not fill up any vessel worse than his stomach. It is sufficient for a person to eat just enough to keep his back straight. If he must eat more, then he can fill a third with food, a third with drink, and leave a third for air." [Sunan al-Tirmidhî (2380)]
Getting Angry
Prophet (peace be upon him) said: "The strong person is not the one who can wrestle someone else down. The strong person is the one who can control himself when he is angry." [Sahîh al-Bukhârî (5763) and Sahîh Muslim (2609)]
Women Putting on Perfume to Go to the Mosque
The Prophet (peace be upon him) said: "Any woman who dons perfume should refrain from attending the `Ishâ' congregation with us." [Sahîh Muslim (444)]
The Prophet (peace be upon him) also said: "Any woman who puts on perfume and then walks by people so they can get a whiff of her perfume is a wanton woman." [Sunan al-Tirmidhî (2786) and Sunan al-Nasâ'î (5126)]