Daf 71a

On Daf 71a it says that if a person calls a fellow Jew wicked, he may go down to his livelihood, and Tosfos brings the explanation of Rav Tzaddok Gaon that the gemara means that he is permitted to burn a third of his produce (שליש תבואתו). But Tosfos is astounded by this explanation and wonders from where the Rav learned this!

But we can explain that when the Rav says שליש תבואתו he means all of his produce which is a third of all his wealth. As Chazal taught on daf 42a: A person should divide up his wealth into three parts - one part in the land, one part in merchandise, and one part in liquid capital. Therefore, the Rav said שליש תבואתו, meaning a third - his produce, and did not write שליש מתבואתו, which would have meant a third of his produce.