Subhanallah they Even say only one testimony of Sahaba is acceptable ,Ibn Hajar al-’Asqalani goes further to say in his Fath al-Bari. Vol. 7, pg. 376:
وفيه قبول خبر الواحد العدل من الصحابة ولو جر ذلك نفعا لنفسه؛ لأن أبا بكر لم يلتمس من جابر شاهدًا على صحة دعواه
This proves that the single testimony of Sahaba is acceptable, even if that is in their own benefit because Abu Bakr did not ask Jabir for any other witnesses to prove his claim.
Alkarbala