“The tithe of the children of Yisrael… I have given to the Levites!” (Bamidbar 18:24)
It is a positive commandment that the children of Yisrael must give a tenth of the seed of the land to the Levites, as it says “For the tithe of the children of Israel, which they set apart as a gift to Hashem, I have given to the Levites!”. This is called “the first tithe”.
Amongst the roots of the commandment are that since Hashem chose the tribe of Levi for His constant service in the temple, it follows that because of His kindness for them He had to give them their livelihood in a respectful manner, as it is fitting for the servers of the King to receive their meals prepared by other people. Even though there are twelve tribes in the nation, and logically they should receive one twelfth of the grain, Hashem added the extra until one tenth to honor them. Since they belong to the royal house it is fitting that their portion should be greater than everyone. It is also a big advantage that their tenth should come to them without any expenditure in the land. A Jew who supports the servants of Hashem with his money, will receive the blessing of Hashem which will take effect on everything that he has. This is what Chazal meant when they said, “Tithes are a fence to keep wealth!”. Chazal also said that it is forbidden for a person to think in his heart that he will test Hashem and see if He will do good to him when he occupies himself with His commandments. About such things it says “Do not test Hashem, your G-d!”. the exception to this rule is this commandment to tithe, in which one is allowed to test Hashem to see if He will bless him when doing it and when being rapid in its fulfilment. This matter is explicit in the words of the prophet, as it says “Bring the tithe to the storehouse, and test me please with this, says Hashem!” (Malachi 3:10)
Amongst the laws of this commandment are that Chazal said that this tithe which goes to the Levite has no sanctity at all, and anyone can eat it, be he priest, Levite or a regular member of the Jewish nation, even in impurity. The only law is that the fruits themselves belong to the Levites.
This commandment applies to men and to women, to priests, Levites and other members of the nation, as even though the Levites take the tithe from the other Jews, they are still obligated to tithe their own fruits in their own grounds. After they have separated this tithe, they may eat it themselves. This commandment of tithing applies biblically only in the holy land, when the whole nation was living there.