Some people said that the name of this great personality was Atiyyah, and some others said that his name was Ata. It is possible that he was Atiyyah ibn Harith al-Kufi al-Hamadani. In any case, he was a great personality from the Tabi‘un who lived in Kufa.
Arbaeen was the day on which the magnetism of Hussein (as) was felt around the world. This magnetism compelled Jabir ibn Abdullah to travel from Medina to Karbala. This is the same magnetism that attracts the hearts and souls of people like you and me, even today, although many centuries have passed since the day of Ashura. Those people who are sympathetic towards the Holy Prophet's (swa) household, forever, retain the love of Karbala in their hearts. The love of Hussein (as), the Master of Martyrs, and his shrine began on that day.
Jabir ibn Abdullah was one of the mujahedeen during the Islamic era. That is to say, before Imam Hussein (as) was born, he was serving the Holy Prophet (swa), and he was fighting beside him. He had seen Imam Hussein's (as) birth and childhood, with his own eyes; and, he had witnessed how he [Hussein (as)] grew to maturity. Jabir ibn Abdullah had definitely seen how the Holy Prophet (swa) coddled Hussein ibn Ali (as): kissed his eyes, kissed his face, fed him with his own hands and gave him water.
Jabir ibn Abdullah had most certainly witnessed these moments with his own eyes; and, Jabir ibn Abdullah had definitely heard, with his own ears, that the Holy Prophet (swa) referred to Hassan and Hussein (pbut) as the "Masters of Youth in Paradise."
After the Holy Prophet's (swa) demise, he bore witness to Imam Hussein's (as) position and character, whether during the time of the caliphs or during the time of the Commander of the Faithful (as), when he was in Medina or when he was in Kufa.
Now, Jabir has heard that Hussein ibn Ali (as) has been martyred. The Holy Prophet's (swa) dear grandchild was martyred while he was thirsty. Jabir set off from Medina--Atiyyah has joined him from Kufa. Atiyyah narrates, "Jabir ibn Abdullah arrived alongside the Euphrates: he performed ghusl there; he wore a clean, white garment; and, then he walked in a slow and respectful manner towards the grave of Imam Hussein (as)."
The narration, which I saw, says: "When he reached the grave, he said three times, loudly, 'Allahu Akbar, Allahu Akbar, Allahu Akbar.' That is to say, when he saw how the Holy Prophet's (swa) and Hazrat Zahra's (sa) dear one was innocently martyred, by oppressive and savage people, he says, "Allahu Akbar." The narration goes on to say: "Jabir ibn Abdullah became unconscious over the grave of Imam Hussein (as) and fell as a result of deep sorrow." We do not know what occurred beyond that moment, but this narration says, when he regained consciousness, he started to speak to Imam Hussein. He said: "Greetings be upon you God's household. Greetings be upon you God's chosen people."
Ayatollah Khamenei, Mar 21, 2006