In Malachi, God said that to not give the tithe was to rob God of what was His.
This passage is a prophet telling the Israelites that they need to be following the Law and tithing.
It is used out of context when used with the New Testament church.
Maybe I miss understood your question. I thought you were comparing someone who gave a 10% tithe (as standed in the OT) which they could well afford, with someone who gave what they could and gave it not to the church but to their needy neighbor.
If this is what you were saying....then this is what I was answering. Comparing the person who gave by the OT tithe standard to the person who gave by the NT standard of giving by grace, what is in the heart and giving to one who is needy, even if it was not as the OT standard.
So under the OT standard God said the tithe was going to Him as a tithe of 10%.
In the NT, Jesus said, that when we give to others we are giving to Him.
In both cases we are giving to Him.
Hope that is clearer because
I agree with you on tithing.