As per Wikipedia:
A tithe (/taɪð/; from Old English: teogoþa “tenth”) is a one-tenth part of something, paid as a contribution to a religious organization or compulsory tax to government. Today, tithes are normally voluntary and paid in cash, cheques, or stocks, whereas historically tithes were required and paid in kind, such as agricultural products.
In Spanish, “tithe” = “diezmo”, and it turns out your tithes could be tax deductible (it doesn’t need to be 10% of your income to qualify), as long as the church you gave it to is registered with the CRA. That’s a reason behind those envelopes found in churches (they tally your contribution so you can get a year-end summary for tax purposes)