It is reported that ‘Abdullaah Ibn Mas’ood (ra) said:

One of the worst sins is when a man says to his brother, “Fear Allaah,” and he replies, “Worry about yourself.”

[Abu Bakr Al-Daynooree, Al-Mujaalasah Wa Jawâhir Al-‘Ilm, 2619]

Bakr Ibn ‘Abdullaah Al-Muzani said:

“If you see someone older than you then respect him saying, ‘He has beaten me to Islaam and righteous action.’

If you see someone younger than you then respect him saying to yourself, ‘I have beaten him in sins’.”

[Al-Bayhaqi, Al-Zuhd Al-Kabeer, p.100]

Ahmad Ibn Harb said:

“There is nothing more beneficial to a Muslim’s heart than to mix with the righteous and to watch their actions, while nothing is more harmful to the heart than mixing with the sinners and watching their actions.”

[Al-Bayhaqi, Al-Zuhd Al-Kabeer, p.100]

Imam Shafi’ee advised one of his students:

“Do not speak about things that do not concern you, for indeed, every time that you speak a word, it takes control of you and you do not have any control over it!”

[Kitaab Al-Adhkaar, by An-Nawawi]

Ibn Bāz said:

❝There is no doubt that increasing Dhikr, seeking Allah’s Forgiveness, and invoking His Blessings and Peace on the Messenger of Allah are of the greatest ways of calming hearts and bringing rest and tranquility to them, having faith in Allah, and removing loneliness, vacillation, and confusion.❞

[Fatwas of Ibn Bāz, The Book of Salah, (11/209, Part No. 11) | Alifta]

Al-Haafidh Ibn Hajar (Rahimahullaah) said: “The happy one is he who clings onto that which the Salaf were upon and avoids that which the latter ones newly invented.” – Fathul-Baari (Page: 253, Vol. 13)

Ibn al-Qayyim (rahimahullaah) said:

“Oh you who spends his lifetime in disobeying his Lord! No one amongst your enemies is more wicked to you than you are to yourself.”

[al-Fawaaid, page 107]

From ‘Alee bin al-Hussain that it was said to him that you are from the best amongst the people but I do not see you eating with your mother?’ He answered: ‘I fear that, if I eat with her, my hand might precede her eye upon some food, so I would have been disrespectful to her! !’ [Collected in ‘al-Birr wa Silaah’ p.82, taken from ‘Akhbar as-Salaf’ p.270] 

Ibnul-Jawzee, رحمه الله تعالى, said: 

“When your companion becomes angry and says something that is unwarranted, you should not take it too hard. His situation is that of a drunken person who is not aware of what is taking place. Instead, be patient, even if it means only for a little while. If you reciprocate his words with harsh words of your own, you become like the sane person who seeks revenge on a madman, or the conscious person who seeks retribution from an unconscious one. Look at him with a merciful eye and pity him for his actions.”

[Sayd al-Khaatir, Pg. 406]

عن أبي موسى الأشعري رضي الله تعالى عنه، قال، قال رسول الله صلى الله عليه و سلم:
“الْمَرْءُ مَعَ مَنْ أَحَب‏”
رواه البخاري و مسلم
On the authority of Abu Musa al-Ash’aree, may Allah be pleased with him, that he narrated that Messenger of Allah (ﷺ) said:
“A person will be with the ones whom he loves”
Reported by Al-Bukhaari and Muslim.