John Calvin Commentary Genesis 33:20

"And he erected there an altar, and called it El-elohe-israel." — Genesis 33:20 (ASV)

And he erected there an altar. Jacob, having obtained a place where he could provide for his family, established the solemn service of God, as Moses previously testified concerning Abraham and Isaac. For although in every place they devoted themselves to the pure worship of God in prayers and other acts of devotion, they nevertheless did not neglect the external confession of piety whenever the Lord granted them any fixed place where they could remain.

For (as I have stated elsewhere) whenever we read that an altar was built by them, we must consider its design and use: namely, that they might offer victims and invoke the name of God with a pure rite, so that by this method their religion and faith might be made known.

I say this so that no one should think that they rashly trifled with the worship of God, for they took care to direct their actions according to the divinely prescribed rule that was handed down to them from Noah and Shem. Therefore, under the word “altar,” let the reader understand, by synecdoche, the external testimony of piety.

Moreover, from this it may be clearly perceived how greatly the love of divine worship prevailed in the holy man; because though broken down by various troubles, he nevertheless was not forgetful of the altar. And not only does he privately worship God in the secret devotion of his mind, but he also engages in ceremonies that are useful and commanded by God.

For he knew that people need help as long as they are in the flesh, and that sacrifices were not instituted without reason. He had also another purpose; namely, that his whole family should worship God with the same sense of piety.

For it is the duty of a pious head of a family to diligently ensure that he has no profane house, but rather that God should reign there as in a sanctuary. Furthermore, since the inhabitants of that region had fallen into many superstitions and had corrupted the true worship of God, Jacob wished to make a distinction between himself and them.

The Shechemites and other neighboring nations certainly had altars of their own. Therefore, Jacob, by establishing a different method of worship for his household, thus declares that he has a God unique to himself and has not degenerated from the holy fathers, from whom the perfect and genuine religion had proceeded. This course would inevitably subject him to reproach, because the Shechemites and other inhabitants would feel that they were despised; but the holy man deemed anything preferable to associating with idolaters.