A.T. Robertson Commentary Luke 18:12

"I fast twice in the week; I give tithes of all that I get." — Luke 18:12 (ASV)

Twice in the week (δις του σαββατου). One fast a year was required by the law (Leviticus 16:29; Numbers 29:7). The Pharisees added others, twice a week between passover and pentecost, and between tabernacles and dedication of the temple.

I get (κτωμα). Present middle indicative, not perfect middle κεκτημα (I possess). He gave a tithe of his income, not of his property.