Ja‘far ibn Muhammad as-Sādiq (702 – 765 AD) (Arabic: جعفر ابن محمد الصادق ), was a theologian, jurist as well as the sixth Twelver and Mustaali Shī‘ah Imām, and the fifth Nizari Imam. His rulings are the basis of the Ja‘farī school of Shī‘ah jurisprudence (fiqh); but he is well respected by both Shī‘as and Sunnis. He is the direct descendant of Muhammad, the Prophet of Islām.
General Quotes 
- Be careful to have truthful friends and try to obtain them, for they are your support when you are in welfare, and your advocator when you have misfortune.
- Majlisi, Bihārul Anwār, vol.74, p.187
- Immorality and surliness makes the human's life miserable and bitter.
- Ibn Shu’ba al-Harrani, Tuhaf al-'Uqul, p.392
- There are three things that signify the magnanimity of a person: good temper, patience, and to avoid aggressive gaze.
- Majlisi, Bihārul Anwār, vol.78, p.232
- Whenever the mind of a person is rectified, he becomes strong and powerful in appearance.
- Majlisi, Bihārul Anwār, vol.78, p.208
- Paying visits to ones own relatives prolongs the life of a person and prevents poverty and indigence.
- Majlisi, Bihārul Anwār, vol.74, p.58
- The person who is aware of the present situations of his time, will never get involved with falsifying and wrongdoing.
- Muhammad Kulayni, Usūl al-Kāfī, vol.1, p.31
- Having the foresight to plan to earn a living, is half of the peace and leisure in life.
- Majlisi, Bihārul Anwār, vol.78, p.204
Regarding Knowledge & Wisdom 
- One who does not use his intelligence will not succeed and one who does not use his knowledge will have no intellect. One who understands will attain nobility and excellence, and one who is tolerant will triumph. Knowledge is a shield (against evil), truth begets honour and ignorance disgrace, understanding is distinction, generosity is salvation and good manners command love and respect.
- Muhammad Kulayni, Usūl al-Kāfī - The Book of Intellect and Ignorance.
- A learned person among ignorant people, is like a live person among the dead.
- Shaykh al-Mufīd, Al-Amali, p.40
- To acquire knowledge is neccessary at all times.
- Majlisi, Bihārul Anwār, vol.1, p.172
- Write knowledge since you can’t memorize unless with writing. Heart confides to the written.
- Majlisi, Bihārul Anwār, vol.1, p.202
- Everything has its tax and the tax of knowledge is to teach its people.
- Being cheerful and affable with people is by itself half of wisdom.
- Majlisi, Bihārul Anwār, vol.76, p.60
- It makes no sense at all if people consider the one who lacks knowledge and science as a prosperous person.
- Ibn Shu’ba al-Harrani, Tuhaf al-'Uqul, p.382
- The person who associates with scholars, will have his reputation exalted.
- Majlisi, Bihārul Anwār, vol.78, p.202
- There are two kinds of scholars: those who act on their knowledge, these are the saved ones; and those who do not put into practise what they know, these are led to their downfall.
- Muhammad Kulayni, Usūl al-Kāfī, vol.1, p.55
- Precision, accuracy and pondering in wisdom and sciences, will nourish and develop a person's brain.
- Majlisi, Bihārul Anwār, vol.78, p.247
- Seek Knowledge and adorn it with forbearance and dignity. Be humble to those whom you teach and to those from whom you learn. Don't be tyrannical in your teaching conduct, for you will forfeit that to which you are entitled to (the reward) on account of it.
- Muhammad Kulayni, Usūl al-Kāfī - The Book of the Merits of Knowledge.
Religous Wisdom 
- The believers have four signs: good humor, tactfulness, kind heartedness and openhandedness
- Muhammad al-Hur al-Aamili, Wasā'il al-Shī‘ah, vol.6, p.321
- A sin that accelerates death and annihilation of man is breaking off paying visits to one's own relatives.
- Majlisi, Bihārul Anwār, vol.74, p.94
- My words are the words of my father, and the words of my father are the words of my grandfather, and the words of my grandfather are the words of my great-grandfathers - Hasan and Husayn; and their words are the words of Ali, and the words of Ali are the words of the Prophet of Allah; and the words of the Prophet are the words of Allah.
- Muhammad Kulayni, Usūl al-Kāfī - The Book of Intellect and Ignorance. Ch.17
- The basis of religion is our affection for the household of the holy Prophet.
- Majlisi, Bihārul Anwār, vol.78, p.183
- Everything has a foundation, and the foundation of Islām is our affection for the household of our Prophet.
- Muhammad Kulayni, Usūl al-Kāfī, vol.3, p.77
- As for ‘Alī ibn Husayn (a), he cried over Husayn (a) for twenty years (after the tragedy of Karbalā); never would any food be placed before him except that he would begin to weep.
- Majlisi, Bihārul Anwār, vol.46, p.108
- God has appionted to the grave of Imām Husayn (a), four thousand anguished and grief-stricken angels, who weep over him (and shall continue to do so) up until the Day of Judgment.
- Ja‘far ibn Muhammad ibn Qulawayh, Kāmil al-Ziyarat, p.119
- Seventy thousand angels worship near the grave of Imām Husayn (a). The prayer (salah) of one of them, is equal to a thousand prayers of mankind. The reward of this prayer is for the visitors of Imām Husayn's (a) grave. The curse of God, His angels and all mankind is forever upon the killers of Imām Husayn (a).
- Ja‘far ibn Muhammad ibn Qulawayh, Kāmil al-Ziyarat, ch.42, p.393
- The one who visits the grave of Imām Husayn (a) knowing his right (of Imāmat), then it is as if he has done the Ziyārat of God on the ‘Arsh (throne).
- Ja‘far ibn Muhammad ibn Qulawayh, Kāmil al-Ziyarat, ch.71, p.192