There were one or two references to tithing before the Law given, correct, but the Law is now non-applicable, and we are under grace. You are obviously trying to convict the church “under the law.” Under grace, it’s about the condition of the heart - of the giver and the givee....and some on both sides of the coin have the proper heart and some on both sides do not.
You might want to peek at the part of the Book that begins with “In the beginning was the Word......” and not just the part that starts with “In the beginning God created the Heavens and the earth...”
Before the Law it was voluntary, not required.
What I wonder more than anything is if these televangelists are willing to share a part of the cash tithe that they take in and share it with widows in their churches?