A little history lesson. In the 8th century people in Europe would
lease land to poorer tenants and those tenants would cultivate the land and then pay rent. It was a common practice back then to calculate 10% of your wages to be used as a payment to your landlord. So it didn’t matter if you had a good month, or a bad month, the rent was always due, and it was 10% of what you made that month. It was basically a kick-back. The landlord owned the land anyway, he was leasing it to you – and so your payment was to give him 10% of what that land made.
Well, as the church increased in size during this time, the church became a landord. Remember the early church used to meet in homes, it never started off as “owning property.” The early church never had any over head. And so now as the church begins to own more and more land, it also becomes a landlord. And now people are giving 10% to the church.
Remember, these were not independent house churches anymore, this was the Roman Catholic Church that started in 380 with Emperor Constantine. And if you didn’t pay your rent, it went all the way to the top. Pretty soon enough of the churches’ tenants were shirking their rent and so in 855 the council of Valence convened and they released this statement:
“This decree deals with the payments of tithes as rent, about which some of the lessees of church lands appear to have been slack, and then urges their general payment by (what does it say next?) all Christians.”
So, in a nut shell, because some people could not pay their rent, the responsibility fell on every church member. And more and more, the tithe became a requirement by law.
And from there you can see how self-serving it was for clergy to convince people that tithing was God’s desire since it is mentioned in the Old Testament.
But, by the 10th century, tithing had faded away as a rent agreement in the secular world and in turn became a legally mandatory practice in the religious world.
So before the 8th century, tithing was a voluntary offering, after the 10th century it had become a legal requirement to fund the state church.
Now, today, tithing has ceased again to be a legal thing, and now it has drifted back to being a moral thing, but many churches still preach it as a requirement for membership, or for church leadership or they use it as a benchmark for spiritual maturity.