Numbers 18:29 You must present as the Lord’s portion the best and holiest part of everything given to you.
When I grew up, I remember a moment the queen came to town. Us kids were told to dress up in our best clothes, as we went out and stood on the road waving at the queen. Likewise, on Sundays we wore our “Sunday best” for church.
Years later, I sometimes find myself wearing a simple T-shirt in church. I have learned that God accepts me as I am. Still, I prefer wearing something nice. I prefer the place of worship to look nice. Why? Not because God would not otherwise accept me, but because it is an act of worship to a most holy God. I want to honour God with the best of what I have. Why dress up for the king (or queen) but act like the kid down the road, for my God?
My God is the King of Kings. He deserves nothing but the best. I do not give Him my left-overs, I give him the best part. I do not give Him the last part of my earnings, after I pay for my rent, food and taxes. I give Him the first part of my earnings.
The tithe is the way to learn to do this, yet notice that God does not deserve just a tithe, He deserves the first tithe. He is first, in everything. When I seek first the Kingdom of God – also in my wallet – then the rest is holy too.