John Calvin Commentary Genesis 28:22

"then this stone, which I have set up for a pillar, shall be God`s house. And of all that thou shalt give me I will surely give the tenth unto thee." — Genesis 28:22 (ASV)

And this stone which I have set for a pillar. This ceremony was a supplement to divine worship, for external rites do not make people true worshippers of God but are only aids to piety. But because the holy patriarchs then had the freedom to set up altars wherever they pleased, Jacob poured a drink offering on the stone, because he then had no other sacrifice to offer. It was not that he worshipped God according to his own will (for the guidance of the Spirit was in place of the written law), but he set up a stone in that place—as he was permitted to do by God's kindness and permission—which would be a testimony to the vision.

Moreover, this manner of speaking, that the stone will be Bethel, is metonymical, as common usage permits us to transfer to external signs what properly belongs to the things they represent. I have recently shown how ignorantly later generations have misused this holy exercise of piety. What follows next regarding the offering of tithes is not merely a simple ceremony, but has a duty of charity connected to it, for Jacob enumerates three things in order:

1. The spiritual worship of God.
2. The external rite, by which he both supports his own piety and professes it before others.
3. An offering, by which he practices giving friendly aid to his brothers and sisters.

For there is no doubt that tithes were used for that purpose.

CHAPTER 29.