Benjamin (the last son of Jacob) did not tithe!

Genesis 45:22

To all of them he gave each man changes of clothing; but to Benjamin he gave three hundred pieces of silver, and five changes of clothing.

Genesis 45:13

And you shall tell my father of all my glory in Egypt, and of all that you have seen; and you shall haste and bring down my father here.

"you shall HASTE and bring down my father here" is the key.

Hebrew: ū·mi·har·tem - hurry, haste

Jacob did not tell "Hey Benjamin, tithing is an eternal moral principle and our family tradition and make sure you tithe 30 pieces of silver to Melichzadek and then come back to Egypt" (The Septuagint says 30 pieces of gold but that is besides the point)

Also it is important to notice that Jacob did not insist Benjamin to pay his tithe out of the 300 pieces of silver 1st before starting the journey. Jacob wasted no time in wrapping up the tents and proceeding to Egypt.

Wondering why neither Jacob nor Joseph within whom the Spirit of God was dwelling, did not teach the "concept of the eternal moral principle" to Benjamin.

Hmmm...... it looks like even Jacob broke his own vow!

Genesis 45:23

And to his father he sent after this manner; ten donkeys laden with the good things of Egypt, and ten she-donkeys laden with grain and bread and food for his father by the way.

Genesis 28:22

And this stone, which I have set for a pillar, shall be God's house: and of all that you shall give me I will surely give the tenth unto you.

Jacob did not bother to tithe out of the good things of Egypt, grain, bread and food!!!