He named that place Bethel (which means “house of God”), although the name of the nearby village was Luz. Then Jacob made this vow: “If God will indeed be with me and protect me on this journey, and if He will provide me with food and clothing, and if I return safely to my father’s home, then the LORD will certainly be my God. And this memorial pillar I have set up will become a place for worshiping God, and I will present to God a tenth of everything He gives me.” (Genesis 28:19-22 NLT)
We find plenty of evidence of the practice of tithing prior to the Law of Moses. Abraham did it. Here we find his grandson, Jacob, making a vow to tithe, if GOd keeps HIs promises of protection and provision. He seems to connect the idea of the tithe with coming back to a place he considers to be the house of God, a place where he had a personal encounter with the Almighty. He connects the act of tithing to the act of worship.