Why did God require tithes from Israel in the Old Testament?

Leviticus 27:30“One-tenth of the produce of the land, whether grain from the fields or fruit from the trees, belongs to the Lord and must be set apart to him as holy.”

Numbers 18:20-24The Lord said to Aaron, “You priests will receive no allotment of land or share of property among the people of Israel. I am your share and your allotment. As for the tribe of Levi, your relatives, I will compensate them for their service in the Tabernacle. Instead of an allotment of land, I will give them the tithes from the entire land of Israel. “From now on, no Israelites except priests or Levites may approach the Tabernacle. If they come too near, they will be judged guilty and will die. Only the Levites may serve at the Tabernacle, and they will be held responsible for any offenses against it. This is a permanent law for you, to be observed from generation to generation. The Levites will receive no allotment of land among the Israelites, because I have given them the Israelites’ tithes, which have been presented as sacred offerings to the Lord. This will be the Levites’ share. That is why I said they would receive no allotment of land among the Israelites.”

The tithes were necessary to support the priesthood—the ordained spiritual leaders who were responsible for Israel’s worship and spiritual life.

Deuteronomy 14:22-23“You must set aside a tithe of your crops—one-tenth of all the crops you harvest each year. Bring this tithe to the designated place of worship—the place the Lord your God chooses for his name to be honored—and eat it there in his presence. This applies to your tithes of grain, new wine, olive oil, and the firstborn males of your flocks and herds. Doing this will teach you always to fear the Lord your God.”

Giving one-tenth of their income to God taught the Israelites to make him a priority, to acknowledge their dependence on him, to keep him a regular part of their lives, and to learn to sacrifice for the well-being of others.