[1] Deuteronomy 14:28–29 provides instructions for the third or poor tithe, which is performed in the third and sixth years of the seven-year cycle.
As described, the tithe should be of grain, wine, and olive oil, but if the distance to Jerusalem made the carriage of these crops unreasonable, the monetary value of the tithe could be brought to Jerusalem instead, and used to purchase anything edible that the owner desired to eat there - an ox, a sheep, some wine, or beer, or "whatever your soul desires" - for a feast with the person's household in the presence of God.
The Talmud and later commentaries reflect a substantial amount of debate about the start and end of the tithing year for various types of crops in various situations.
After the Second Temple's destruction and the inability to consume fruits of Second Tithe in a state of ritual cleanness, the general practice was to redeem the produce and its sanctity on a coin, and to discard the coin, or else to separate the Second Tithe and to profane its sanctity by having it transferred to a smaller piece of produce of its own kind, such as wine upon wine and grain upon grain.
Every three years, on the mincha (afternoon service) of the last day of Pesach (Passover), they would say the Vidui Maaser (a confession of tithing prescribed specifically in the Torah).
The reason this is done at the end of the festival, at the last prayer is because until that time (during the Temple era), people were still eating their Maaser Sheni.
The Jewish Encyclopedia article (1911) concludes that there is no significant textual evidence that the tithes come from different sources and the theory ignores the role of terumah and terumat maaser, which were separated for the priests.
In both alleged "versions" it is required that a portion be given to the Leviim because they had no inheritance of land, unlike the other tribes, and were considered to be more likely to be supported by others' property.
[14] This is in contrast to the reading of the text which was a warning by Samuel to the Children of Israel about the abuses of power that a king may impose.
Some scholars speculate that these tributes began to be used for public festivals, often including religious ones, and thus gradually came to be seen as associated with the priests.