Maaser Rishon

The first tithe (Hebrew ma'aser rishon מעשר ראשון) is a positive commandment in the Torah requiring the giving of one tenth of agricultural produce, after the giving of the standard terumah, to the Kohen (Jewish priest) (or Levite). This giving is required to be free of both monetary and servicial compensation.

Historically, during the First Temple period, the first tithe was given to the Levite. Approximately at the beginning of the Second Temple construction, Ezra and his Beth din implemented its giving to the kohanim.

The tithe gift is discussed in the Hebrew Bible (Numbers 18:21-26) according to which a tenth of the produce was to be presented to a Levite who then gave a tenth of the first tithe to a kohen (Numbers 18:26). Tithing was seen as performing a Mitzvah done in joyful obedience to God. Giving tithe would open oneself up to receipt of divine blessing

The Torah instructs that the tithe should be of the "five grains",wine, olive oil, fruit, and cattle (Leviticus 27:30-33). The time for taking such tithes was at the finished stage of processing the produce (Numbers 18:30). Unlike Terumah given to the Kohen, the Maaser Rishon was not regarded as sacred, and as a result did not have to be ritually pure, neither was it required to be eaten in any particular state (such as the Temple in Jerusalem). Once received by the Levite, it was regarded simply as ordinary property, and they could pass it on to non-Levites, or sell it, as they wished.

Traditionally tithes were calculated for the produce of each whole year, however Chazalic Literature indicates that there was a debate between Beit Shammai and Beit Hillel as to when this tithing year should begin and end. Tithing years had different starts and ends depending on the particular crop in question; land crops began their tithe year on the first of Tishrei (Rosh Hashanah); according to Eleazar Kalir and Simeon bar Yohai the first of Tishri was also the start of the tithe year for cattle, but according to Meir Lublin it was the first of Elul that held this honour. The followers of Hillel argued that the tithe year for fruit from trees began on the fifteenth of Shevat, but the followers of Shammai, his rival, argued that it began on the first of Shevat; the view of Hillel's followers eventually became the majority view and the new year for trees — Tu Bishvat — is now held at the date which they considered appropriate.

...
Wikipedia