Some of the speeches of Amir Al-Mo’mineen in this regard have indicated that during his caliphate Fadak was returned to him and was in his hands as he says:
“Yes, from all that the sky casts its shadow upon, the only thing that was in our hands was Fadak which a group unjustly took and another group generously forgave them and liberally ignored the matter. Truthfully it is God who is the best judge...” 
By considering these words at face value, it may be believed that Fadak during this period of caliphate was returned to his excellency and was in his hands. But in our opinion this conclusion seems unlikely especially since what has been mentioned in the Nahjul Balagha was during the time of his own caliphate and written in the past tense and so this indicates what is being said is about the state of Fadak prior to that time.
In any case, those occurrences that have been noted in history cannot be a witness to how he dealt with the case of Fadak and it is not to be assumed from this that it was returned to its truthful owners – who were the heirs of Hazrate Fatemah (sa) - or that they were given time to reap benefit from it even that it was left in the same state that he found it.
 – Nahjul Balagha Letter 41