Albert Barnes Commentary Deuteronomy 26:12

"When thou hast made an end of tithing all the tithe of thine increase in the third year, which is the year of tithing, then thou shalt give it unto the Levite, to the sojourner, to the fatherless, and to the widow, that they may eat within thy gates, and be filled." — Deuteronomy 26:12 (ASV)

See the marginal reference to Numbers and note. A strict fulfillment of the onerous and complicated tithe obligations was a leading part of the righteousness of the Pharisees: compare (Matthew 23:23).