You shall set aside a tenth part - This is what is written in the Sifri: "You shall set aside a tenth part of all the yield of your sowing that is brought from the field every year" (Deut. 14:22) [from a superficial reading] I can only find that one is obligated to tithe the yield of sowing, from where do I know that he is obligated on tithing also on interest and merchandise and all other types of gain? The text says "all" - it could have said simply "the yield of your sowing", why [does it have the word] "all"? To include interest and merchandise and all other types of ways of gain. And this too is in the Hagadah (?): "that is brought from the field every year" - that is to say if you don't tithe your field properly, you will be left only with "what comes from the field", meaning, your field only produces according to the tithes that were taken previously, therefore, "what comes from the field" - that is to say what you were used to take to tithing from the field. A story: a certain rich man who had a field that produced a thousand kor, and that same rich man gave 100 kor for tithes, and he separated this every year, and did so all his days. When he got sick to the point of dying he called his son and said to him: 'my son, know that this field that I am giving you for inheritance gives a thousand kor every year, make sure that you will separate 100 kor as I did'. Then he died. His son stood on his place and the field produced a thousand kor as it did when the father was alive, and [the son] separated 100 kor. In the second year the son looked and understood that tithing was a great thing. He said: 'We will not separate for the next year' And the field diminished [its production] and produced only 100 kor. He was disappointed, and his relatives heard that the field diminished and that he did not separate the tithes. They all came together near him, wearing white and happy. He said to them: 'I am under the impression that you are happy with my disgrace.' They said to him: 'We are disappointed in you since you brought upon yourself all this disgrace, and why did you not separate the tithe as it would have been right to do? Come and see that in the beginning, when the field first came to your hands,you were the owner of the house and the Holy One of Blessing was your kohen, whose part [in your field] was the tithe to be given to the poor and now that you didn't separate the part of the Holy One of Blessing, the Holy One is the master of the house and you are His kohen, in that your field will not do the thousand kor it did in the beginning, when you did separate the 100 kor. And this is why it's written "to each man his holy things will be his [and whatever he gives to the kohen will be his]" (Numbers 5:10) - that is to say, when he does not separate as appropriate the only thing that will be his is his holy portion, that is, the tithe. And on this our sages said: 'the one who delays his tithes will in the end have only one tithe, as it is written '[For ten acres of vineyard shall yield one bat] the seed of a homer will yield an ephah' (Isaiah 5:10). The tithe of an ephah is is three se'ahs and in a homer there are thirty se'ahs and it is written 'For ten acres of vineyard shall yield one bat' and Rav Natan Haophaniel (?) explains 'what comes out of the field' that is - if not, if you do not separate the tenth will be for the one that comes out to the field, which is, the wicked Esav, which is: the idolaters will get it.