The promise is to the nation of Israel as a whole; not to each individual Israelite. When God’s people were faithful in their giving, the nation would prosper. That does not mean that faithful children of God who faithfully paid their tithes would never suffer economic hardship (Mark 12:42–43). But when the faithful nation was blessed, those to whom much was given were commanded to share their abundance with those who received little. In this way, God ensured that no Israelite would lack the necessities for daily life.
10 Bring the full tithe into the storehouse, that there may be food in my house. And thereby put me to the test, says the LORD of hosts, if I will not open the windows of heaven for you and pour down for you a blessing until there is no more need.