11. How seriously does the Bible consider unfaithfulness in tithes and offering?

Failure to return tithe is a breach of covenant relationship with God. Not only does it put our temporal blessings in jeopardy, the promise of redemptive grace from God also becomes void. JTL25 13.1

In contrast to the generosity and faithful giving of the early Christians in Jerusalem (Acts 4:32), Ananias and Sapphira plotted together to withhold a large portion of the proceeds from the sale of a piece of real estate, which they had pledged to give entirely to the Lord. Their deception in the matter was met with swift and terrible judgment. Each lied to Peter when questioned about the matter and each was struck dead (Acts 5:1-11). This judgment was a powerful reminder to the fledgling church that God detects hidden sin, and that He will not be mocked or robbed. JTL25 13.2