Rabbi Yehoshua ben Levi said: Biblically, it is considered hefker even if his declaration was only in front of one person. Why was it decreed upon that it should be in front of three? It is in order for there to be one person who will take possession and two people to testify to this.

The Rishonim ask from the Mishna that we learned above (43a), which stated: If a person vowed not to have benefit from someone and these two people were walking together on the road, and the person who cannot benefit from his friend had no food, the halacha is that if there is nobody else around, he can put the food on the rock or fence and say, “These are ownerless for anyone who wants to take them.” The other person can then eat. If they are the only two present, it should not be regarded as hefker?

The Ritva answers that the Rabbis were lenient in a case where there was an extreme necessity to provide the person with food. They ruled in this case that the Biblical law stands and the hefker is valid.

The Bach answers that even when there are not three people present, the hefker is valid. The Sages instituted that he can retract from his hefker declaration if three people weren’t present. However, as long as he did not retract, the hefker is completely valid.

The Shach cites Tosfos that the Rabbinical decree requiring three people to be present was only said in regard to the hefker of land; however, regarding movables, such as food, it does not apply.