Ja’far ibn Muhammad (AS) known as the Ja’far as-Sadiq (AS) is the sixth Shiite Imam. Imam Sadiq (AS) was born on 17 Rabi al-Avval 83th (702 CE) in Medina. His father, the previous Imam, was named Muhammad al-Baqir (AS) and his mother was called Umi-Farvah. After his father, Imam Sadiq (AS) became the Imam of the Shias and his leadership lasted for about 34 years. The era of Imam Sadiq (AS) was the time of instability and wars, since the Umayyad dynasty were weakened so much due to the battles they had in the Islamic territory. In addition , Abbasid dynasty were trying to topple the Umayyad government and reign over the whole Islamic world. The weakness of the rulers gave Imam Baqir (AS) and Imam Sadiq (AS) a perfect opportunity to spread the teachings of Shiism and train so many Shia scholars. At last, Imam Sadiq (AS) was martyred by the order of the Mansur (an Abbasid Caliph) on 148 H (765 CE). 

What does “Sadiq” mean?

The word “Sadiq” means an honest person who does not tell lies. 
Once, Imam Sajjad (AS), the grandfather of Imam Sadiq (AS) was asked: “Who is the Imam after you?”
“My son Muhammad (AS) who opens knowledge and after him his son Jafar who is called in the skies as ‘Sadiq’” Imam Sajjad (AS) replied. 
He was asked once more: “Why out of you all, he is called “Sadiq” while you all are honest?”
Imam Sajjad (AS) said: “Because the Prophet (PBUH & HP) said: ‘Name my son Jafar ibn Muhammd as “Sadiq” because there will be another Jafar in the future who falsely claims to be an Imam and he is named “liar” by Allah’” (On the contrary, Jafar ibn Muhammad is honest because he is a true Imam). (1)
The liar Jafar mentioned in the hadith is the son of Imam Hadi (AS), the eleventh Imam. 

The knowledge of Imam Sadiq (AS)

All Shiite Imams were known for their abundant knowledge in their time; but among all, Imam Baqir (AS) and Imam Sadiq (AS) were different. Due to the fact that Umayyad dynasty were weak and unstable in those times, Imam Baqir (AS) and Imam Sadiq (AS) had this chance to unveil the abundant knowledge of the Prophet’s household. 
About 4000 people learned from Imam Sadiq (AS) and narrated hadiths from him . (2)
Amr ibn Abi al-Mighdam, a Sunni scholar, says: 
“Every time I looked at the face of Jafar ibn Muhammad (AS), it would make me sure that he is a descendant of the prophets. Once, I saw him in Jamrah (a place in Mecca where the pilgrims gather) and he was telling people: ‘Ask me! Ask me!’” (3)
Hassan ibn Ali al-Vasha, a Shiite hadith narrator, says:
I saw about 900 sheikhs who all would narrate hadiths from Jafar ibn Muhammad (AS) (4).
Once Abu Hanifah, one of the most knowledgeable and popular Imams of the Sunnis, was asked: “Who do you think is the most knowledgeable person in religious fields?” he said: “I do not know anyone more knowledgeable than Jafar ibn Muhammad (AS)” (5).
Imam Sadiq (AS) is mostly known for his knowledge in Islamic laws and because of this, the Shiite school of law is called “Jafari School”. The hadiths narrated from Imam Baqir (AS) and Imam Sadiq (AS) are more than all the hadiths narrated from the Prophet (PBUH & HP) and the other Imams all combined together.

The moral attributes of Imam Sadiq (AS)

In addition to his wisdom and knowledge, Imam Sadiq (AS) was also known for his significant moral qualities. 
Muhammad ibn Talha says: 
“Imam Sadiq (AS) was the greatest person among the Prophet’s household and he was so knowledgeable and he would pray and recite the Quran so much and he was an ascetic person.” (6)
Malik ibn Anass, one of the Sunni school’s head, says: 
Every time I met him, he was in one of these three moods: either praying, fasting or whispering prayers (7).
Hisham ibn Salim, a famous apprentice of Imam Sadiq (AS) says:
Abu-Abdillah (Imam Sadiq (AS)) would always take a bag full of bread, meat and money in the darkness of the nights and go to the house of the needy ones in Medina and give it to them while they didn’t know him. Then, when he died, the people weren’t given those goods anymore and from that, they found out about his identity. (8)

Resources 

1.  Al-Khara’ij, ar-Ravandi, vol.1, pg.268
2.   Al-Irshad, Sheikh Mufid, vol.2, pg.179
3.    Siar A’lam an-Nubalah, Zahabi, vol.6, pg.257
4.    Rijal al-Kashi, vol.1, pg.138-139
5.   Siar A’lam an-Nubalah, Zahabi, vol.6, pg.257
6.    Kash al-Qummah, Irbeli, vol.2, pg.691
7.  Bihar al-Anvar, Majlesi, vol.47, pg.16
8.   Kafi, Koleini, vol.4, pg.8
    

“I have not been sent except to elevate the morality” [1] Morality is such an invaluable asset for humans in this worldly life and the Hereafter that Prophet Muhammad (PBUH&HP) has introduced it as the only goal of his prophetic mission. It is also noticeable in the following verse of the Quran that Prophets were sent by Allah to improve humanity:

“Allah certainly favored the faithful when He raised up among them an apostle from among themselves to recite to them His signs and to purify them and teach them the Book and wisdom, and earlier they had indeed been in manifest error” (3:164)

Moreover, humans naturally seek and look up to role models who have successfully personified all the perfect qualities. One of the shining examples of such models to follow is undoubtedly the last Messenger of God, Muhammad (PBUH&HP) who possesses all the best personality traits:

“and indeed you possess a great character” (68:4)

“There is certainly a good exemplar for you in the Apostle of Allah (i.e., Muhammad (PBUH&HP))” (33:21)

Let’s have a glimpse at some of his most prominent characteristics in this short article:

1. Honesty

Prophet Muhammad’s (PBUH&HP) truthfulness and honesty were so famous among his most noble attributes, from his tender age and before he was chosen as the Messenger of God, that the people of that time would call him al-Amin (the trustworthy).

This characteristic of his reached the extent that almost everyone in Mecca would put their money, valuables, and savings in the hands of Prophet (PBUH&HP) for safekeeping. Even, after he was called for prophethood, despite all their hostility to him, the Quraysh[i] continued depositing their treasure with him.

2. Simple living

In spite of all his responsibilities as a prophet, Muhammad (PBUH&HP) would do all his chores himself as well as helping his family with the household work; he used to patch his clothes, mend his shoes, and milk his goat with his own hands. He would eat simple food, wear simple clothes and travel in a simple manner.

It is not that he could not afford a luxurious lifestyle; there were stages in the prophet’s (PBUH&HP) life when he had a reasonable income from his trading. In fact, he chose to lead a simple life. He preferred to live on what was sufficient and as normally as any other simple Muslim. When he acquired great wealth, he did not hold on to it for himself. Instead, he gave it to the poor and spent it for the good of society.

3. Regularity and Cleanliness

Prophet Muhammad (PBUH&HP) showed great orderliness in all aspects of his life, from his personal matters to all social, political, and economic affairs. He paid attention to his appearance, and was much fond of using perfume and spent so much money on that; he also encouraged his followers to do the same and to keep their bodies and houses clean.

One of the high values taught by the prophet (PBUH) was regarding the importance of time. He urged people to choose the right moment for carrying out specific activities; he would divide his day into three parts, one for saying prayers to God, one for his family, and a portion for himself, which he would share with people. He has mentioned in a narration about self-discipline that “God loves it if any of you does a job, he/she does it perfectly” [2].

4. Kindness

In his social life as well as his family life, prophet Muhammad (PBUH&HP) was always kind, affectionate, and respectful to people. He was known to have a pleasant smile on his face which never faded away. He took the lead to extend greetings to those he knew and those he did not know, including children and slaves.

The holy prophet (PBUH&HP) also showed significant love and tenderness to children; he seated them on his lap, put them on his shoulders, and kissed them. He was incredibly kind to his slaves too. He told people that the slaves were their brothers. He took a great interest in the welfare of all people, had great compassion for people in trouble, and would do his best to remove their sufferings [3].

5. Respect for women

Women in pre-Islamic Arabia would face nothing but neglect from society; all their personal and societal rights were disregarded to the extent that killing and burying female infants alive was a prevalent practice among them. But Islam, from its very beginning, recognized the importance of women and considered the lives of both men and women to be precious.

Prophet Muhammad (PBUH&HP) commanded others to fulfill women's rights and to honor their individuality, and he showed a particular form of respect towards women himself while implementing these principles. An example of his respect towards women is his being helpful to his wives. He has said in this regard: “Beware, the best of you is he who is the best towards his women, and I am the best among all of you toward my women” [4].

Along with these few traits, he possessed so many other significant characteristics that anybody wishes to attain. His life was full of examples of perseverance, modesty, generosity, piety, love, mercy, forbearance, bravery, and many many other ones. Admittedly, that’s why God and His angels bless our Holy Prophet (PBUH&HP):

“Indeed Allah and His angels bless the Prophet; O you who have faith! Invoke blessings on him and invoke Peace upon him in a worthy manner” (33:56)

Notes:
[i] A powerful merchant tribe that controlled Mecca and its Kaaba and that according to Islamic tradition descended from Ishmael. Prophet Muhammad (PBUH) was born into the Banu Hashim clan of the Quraysh tribe.

Reference:

1. Shaykh Ali Namazi, Mustadrak Safinat al-Bihar, volume 1, page 410
2. kanz ul amal: 9128
3. the last prophet
4. prophet Muhammad (PBUH&HP)
5. who is Prophet Muhammad