Paul told the Thessalonians that the Lord would avenge the victims of fraud.

Source:

1st Thessalonians 4:6

Another form of fraud was merchants using different weights and measures to shortchange customers. Who originally forbade this?

Fraud continued in the early church. This couple lied about their offerings. What happened to them?

After Ananias and Sapphira each lied to Peter, then God struck them dead .

Source:

Acts 5:1-11

It was Moses. He forbid this in the name of God. Merchants must use honest weights and measures for all.

Source:

Leviticus 19:35-35 and Deuteronomy 25:13-16

In spite of the example of Hophni and Phinehas other priests continued substandard service to God. In Malachi God complains that the priests are despising his name. How do the priests do this?

The priests offered blemished animals for sacrifices instead of the unblemished ones God required.

Source:

Malachi 1:6-14