a) The Second Tithe

After setting aside the first tithe one sets aside a tenth of the remainder; this is called the second tithe (but in the third and sixth years of the sabbatical cycle it is given to the poor). When the Temple exists it should be eaten in Jerusalem, as it says "And you shall eat before Ha-Shem your G-d in the place that he shall choose... the tithe of your grain, wine and oil"¹; or it can be redeemed (outside Jerusalem) for 5/4 of its value and the proceeds used to buy food to be eaten in Jerusalem [as it says "And if the way is too long for you... you may put [it] into money...] and you may give the money for anything that you desire... and eat there...".¹ When the Temple does not exist it can still be redeemed outside Jerusalem, not necessarily for its full value, and the thing that it is redeemed for must be destroyed. It is forbidden to eat it outside Jerusalem (rabbinically, even if it has never been there), as it says "You shall not eat the tithe of your grain, wine and oil in your gates".^2,a

A person who is impure or uncircumcised or who has just lost a close relative is forbidden to eat the second tithe in Jerusalem (and rabbinically, even outside), as it says "I have not eaten it while in mourning and have not consumed it while impure".³ Similarly, one may not consume the second tithe if it has become impure; one must then redeem it, even in Jerusalem. It is forbidden to redeem it for anything that cannot be used for eating, drinking, or anointing, as it says "And have not given it to the dead"³ -- that is, have not used it for anything that does not sustain the body; and it cannot be used for any commercial purpose.^b

On the last day of Pesach in the fourth and seventh years of the sabbatical cycle, after all the tithes of the preceding year have been consumed, we are commanded to recite the "confession of the tithes", as it says "When you have finished tithing all the tithes of your crops in the third year... you shall say before Ha-Shem your G-d `I have cleared out the sacred things from the house'...".^4,c

b) The Fruit of the Fourth Year

The fruit of a tree in the fourth year after its planting (or grafting) must be eaten in Jerusalem like the second tithe, as it says "And in the fourth year all its fruit shall be holy for rejoicing to Ha-Shem"⁵; no offerings or tithes or gifts to the poor are given from it.^d

Sources:
1. Deut. 14:23-26	a. 1:1, 2:1-3,5-6; 5:1
2. Deut. 12:17	b. 3:1-5,10,17; 7:3
3. Deut. 26:14	c. 11:1-3,7,12
4. Deut. 26:12-13	d. 9:1,4; 10:14
5. Lev. 19:24