Authoritativeness of the Solitary Report of a Truthful Narrator

we were with Abi Basir when Amr b. Ilyas came and said to him: O Aba Muhammad (i.e. Abi Basir) my brother is in Halab (Aleppo), he sent me some wealth as Zakat so that I can distribute it in Kufa, but the road was cut-off on him [brigands stole it] – do you have a narration about this? he said: yes, I asked Aba Ja’far عليه السلام this question and I don’t think anyone else has asked me about it before, I said to Abi Ja’far عليه السلام: may I be made your ransom, a man sends his Zakat from one land to another but it is intercepted on the road, he said: he is excused but if it were me I would have repeated again [giving Zakat a second time].