The verb dekatoō means to tithe — either to collect a tithe from someone or to pay a tithe. It appears twice in Hebrews 7 (vv. 6 and 9) in the argument about Melchizedek's superiority to the Levitical priesthood. The verb highlights the transactional and covenantal nature of tithing as a recognition of someone's superior priestly authority.
The theological argument of Hebrews 7 using dekatoō is sophisticated: Levi was 'in the loins of Abraham' when Abraham tithed to Melchizedek — therefore Levi himself, through his ancestor, paid tithes to Melchizedek, demonstrating that Melchizedek's priesthood is superior to the Levitical. This establishes that Christ, as a priest in the order of Melchizedek (Psalm 110:4), holds a priesthood superior to that of Aaron and Levi. Tithing thus becomes not merely a practice of generosity but a theological statement about the nature of Christ's priesthood and sacrifice.