Among `Ali’s sayings narrated by Abu Nu`aym with his chains:
From al-Husayn ibn `Ali:
"The most sincere of people in their actions and the most knowledgeable of Allah are those who are strongest in their love and awe for the sanctity of the people of lâ ilâha illallâh."
From `Abd Khayr:
"Goodness does not consist in having much property and children, but in doing many good deeds, increasing your gentle character, and adorning yourself before people with the worship of your Lord. Then, if you do well, glorify Allah; if you do ill, ask forgiveness of Him. There is no good in the world except for two types of people: someone who sins and then follows up with repentence, and someone who races to do good deeds. What is done in Godwariness is never little, and how can something be little if accepted by Allah?"
From Abu al-Zaghl:
"Remember five instructions from me in following which you shall sooner exhaust your camels than run out of their benefit:
let no servant hope for anything except from his Lord;
let him not fear anything except his own sin;
let no ignorant person feel ashamed to ask about what he knows not;
let no knowledgeable person, if asked about what he knows not, feel ashamed to say Allah knows best; and
patience is in relation to belief like the head to the body, one has no belief if he has no patience."
From Muhajir ibn `Umayr:
"What I fear most is the hankering after idle desires and long hopes. The former blocks one from the truth and the latter causes forgetfulness of the hereafter. In truth the world has gone its way out, in truth the hereafter has come journeying to us û and each of the two has its own sons. Therefore be a son of the hereafter and do not be a son of the world! Today there are deeds without accounts, and tomorrow, accounts without deeds."
From Abu Araka:
"I have seen a remnant of the Companions of Allah’s Messenger. I see no-one that resembles them. By Allah! They used to rise in the morning disheveled, dust-covered, pale, with something between their eyes like goat’s knees, as they had spent the night chanting Allah’s Book, turning from their feet to their foreheads. If Allah was mentioned they swayed the way trees sway on a windy day, then their eyes poured out tears until û by Allah! û they soaked their clothes. By Allah! It is as if folks today sleep in indifference."
From al-Hasan ibn `Ali:
"Blessed is the servant that cries constantly to Allah, who has known people while they have not known him, and Allah has marked him with His contentment. These are the true beacons of guidance. Allah repels from them every wrongful dissension and shall enter them into His own mercy. They are not the wasteful tale-bearers nor the ill-mannered self-displayers."
From `Asim ibn Damura:
"The true, the real faqîh is he who does not push people to despair from Allah’s mercy, nor lulls them into a false sense of safety from His Punishment, nor gives them licenses to disobey Allah, nor leaves the Qur’an for something else. There is no good in worship devoid of knowledge, nor in knowledge devoid of understanding, nor in inattentive recitation." This is comparable to al-Hasan al-Basri’s own definition: "Have you ever seen a faqîh? The faqîh is he who has renounced the world, longs for the hereafter, possesses insight in his Religion, and worships his Lord without cease."
From `Amr ibn Murra:
"Be wellsprings of the Science and beacons in the night, wearing old clothes but possessing new hearts for which you shall be known in the heaven and remembered on the earth."
"This world lasts for an hour: Spend it in obedience."
"Thus does Knowledge die: when those who possess it die. By Allah, I do swear it! The earth will never be empty of one who establishes the proofs of Allah so that His proofs ans signs never cease. They are the fewest in number, but the greatest in rank before Allah. Through them Allah preserves His proofs until they bequeath it to those like them (before passing on) and plant it firmly in their hearts. By them knowledge has taken by assault the reality of things, so that they found easy what those given to comfort found hard, and found intimacy in what the ignorant found desolate. They accompanied the world with bodies whose spirits were attached to the highest regard. Ah, ah! How one yearns to see them!"
Source: http://www.sunnah.org/publication/khulafa_rashideen/caliph4.htm