Abdullah ibn Ja'far (Arabic: عبد الله بن جعفر) (c.624-c.699 or 702/704)  was a companion and relative of the Islamic prophet Muhammad, a nephew of Ali ibn Abi Talib and a half-brother of Muhammad ibn Abu Bakr. He was loyal to Ahl al-Bayt in spite of his absence at the Battle of Karbala. He is reported to have said: ”Thanks to God Almighty, I could not support al-Husayn ibn Ali at Karbala, but my two sons (’Awn and Muhammad) did. According to Richard Francis Burton he is widely recognized as the most sympathetic amongst Arabs. His grave is situated near Aqeel ibn Abi Talib and Abu Sufyan bin al-Harith (the grandson of Abd al-Muttalib) in Janatual Baqi)
He was the son of Ja'far ibn Abu Talib and Asma bint Umais. They had emigrated to Abyssinia in 616, and Abdullah and his two brothers were born there.:196 Abdullah was the first of Muslims to be born in the land of Abyssinia  After birth of Abdullah in Abyssinia (Habesha Presently Ethiopia), king of the Kingdom of Aksum ( Al-Najashi) was blessed with a son too. He immediately asked the parents of Abdullah Ibn Jaffar about the name of their child. Upon knowing the name of Jaffar family, King of Abyssinia also chose the name “Abdullah” for his first son. It is also stated that Asma bint Umays was the nursing mother of son of Abyssinian King. The younger brother of Abdullah appears to be the first child in the Muslim history who was named Muhammad after the Prophet of Islam. The family returned to Arabia in 628 and settled in Medina.:196
In addition to Ibn Hajar' reference, it is said that after 3 days of Jafar’s death Muhammad went to house of Asma and called for children of Jafar. He then said about each of them “As for Muhammad, he resemble our uncle Abi Talib. As for Abdullah, he resembles me in terms of both my appearance and character. Afterward, Muhammad took the right hand of Abdullah and said “O Allah, provide a successor for Jafar in his family, and bless Abdullah in his business, and repeated this appeal to Al-mighty thrice. Muhammad instructed the sons of Abi Talib, namely Jafar, Aqeel and Ali that they should arrange marriages of their children with their cousins.
According to Shaikh Muhammad Abbas Qummi, he had 20 sons from different wives, including 5 children from Zainab Binte Ali. Daira-e-Maarif Islamia (Circle of Islamic Knowledge) of University of Punjab (pages 568-70, Vol.X) describes that Zainabi is a progeny of Abdullah’s son Ali through Zainab binte Ali:31
It is related that Zainab already forecast the journey (journey to Karbala) before her marriage and permission for accompanying with her brother was obtained during marriage negotiations. With regard to Absent of Abdullah in battle of Karbala, it is said it was due to his poor eye sighting consequently he was unable to bear the rigidities of journey and war.:37 Knowing Hussain’s journey to Kufa, Zainab, the wife of Abdullah ibn Jaffar begged her husband’s permission to accompany her brother. Realizing anxiousness of her husband she stated that:
You know that for 55 years my brother and I have never been separated. Now is the time of our old age and the closing period of our lives. If I leave him now, how shall I be able to face my mother, who at the time of her death had willed, “Zainab” after me you are both mother and sister for Hussain? It is obligatory for me to stay with you, but if I do not go with him at this time, I shall not be able to bear the separation.
Abdullah then granted his permission and sent their two sons for the destined journey.
Abdullah was concurrently married to Layla bint Masud.:300 With reference to books ‘Nasab e Quraish Page-83’ and ‘Jameerath ul Nasab by Ibn Hazm page 62’ it is described that Layla Binte Masood bin Khalid was “Zoja-e-Sani (second wife)” through this marriage he had two daughters (Umme Muhammad and Umme Abhiha) and four sons (Yahya, Haroon, Suleh & Musa).
Battles:With regard to his presence in the Battle of Camel, it is indicated that at the end of Battle, while entrusting the return of Aisha to Medina under security of her brother Muhammad ibn Abi Bakar, Ali ordered for payment of 12,000 Dirhams to Aisha. Abdullah thinking that the amount was too little, brought out a larger sum for Aisha.:127 According to Ahmad ibn A'tham in battle of Siffin he was commanding the infantry in the army of Ali ibn Abi Talib together with his cousin Muslim ibn Aqeel, Muhammad ibn Al-Hanafiyyah and step brother Muhammad bin Abi Bakar.
Politics:He was a staunch supporter of his uncle Ali in the civil war. He maintained a reputation for liberality and patronage in Medina, earning him the nickname “the Ocean of Generosity”. After killing of Ali Ibn Abi Talib, Abdullah bin Jaffar together with his cousins Hassan and Hussain participated in washing the body and dressed him for burial in three robes without a Kurta (a long shirt).
In addition to some spy reporting to Ali Ibn Abi Talib that Qays bin Sad bin Ubadah, his governor at Egypt had given allegiance to Muawiya, he received his letter which was written in perspective of affairs emerged on account of a conspiracy caused by opponent of Ali. Ali called his sons and Abdallah bin Ja'far and consulted the matter. Upon advice of Abdullah, Ali wrote a letter ordering Qays bin Sad to seek the people to give their allegiance as the Muslims have done (after the 3rd Caliph). But, if they do not, then fight them. The governor of Egypt against this communication wrote a letter to Ali Ibn Abi Talib. Then Abdullah Bin Jaffar requested his father in law to replace Qays bin Sad bin Ubadah with Muhammad ibn Abi Bakr as governor of Egypt and pleaded that if he really has gone over to Mu`awiyah, he will refuse to give up Egypt. However, according to Tabari it was a poor advice consequent to meeting of Qays bin Sad with Ali during the period of killing of Muhammad bin Abi Bakar.:185–189 (VOL.XVI)
Once a Chief of Iraqi village asked Abdullah Bin Jafar to recommend his case before Caliph Ali for accomplishment. He did so and matter of that chief was satisfied by Ali Ibn Abi Talib. As a gratification the chief sent 40,000 Darhims through some people to Abdullah, who refused the money saying that we do not sell our good deeds
Knowing death of his two sons in the battle of Karbala, people were offering condolences to Abdullah, one of his Mawili (Abu al-Lislas [a companion]) said that “this is what we have met and what has come upon us through Hussain Ibn Ali” on this statement he struck him with his sandal and told that I am pleased that my two sons killed with my brother and cousin. By God! If I had been present with him, I would have preferred not to leave him in order that I would be killed with him. He then seeking attention of people consoling him, said that “Praise be to God, Who has made life hard, console Hussain Ibn Ali with my own hands, my two sons consoled him. :177
According to Ibn Khaldun in chapter 2 volume II title “Yazid-I” from 60 to 64 AH, it is described that Abdullah sent a letter through his sons Awn & Muhammad, to Hussain, requesting that “for God sake come back. It is my advice to you in anxiety that you would be killed and Ahle-Bayt destroyed. As a result, earth’s light will come to an end, there would be no leader for Muslims. Please do not hurry in journey, I would be reaching there after this letter." Later he went to Amr bin Said who was Yazid's governor of Mecca and asked him to write a letter to Hussain offering him a guarantee of harmless behavior assuring him kindness and open-handedness. "Show trust to him in your letter and request him to return." This letter was replied by Hussain too.