John Calvin Commentary Genesis 28:17

"And he was afraid, and said, How dreadful is this place! This is none other than the house of God, and this is the gate of heaven." — Genesis 28:17 (ASV)

And he was afraid, and said. It seems surprising that Jacob should fear when God spoke so graciously to him; or that he should call that place “dreadful,” where he had been filled with incredible joy. I answer, although God exhilarates His servants, He at the same time inspires them with fear, so that they may learn, with true humility and self-denial, to embrace His mercy.

We are not therefore to understand that Jacob was struck with terror, as reprobates are, as soon as God shows Himself; but he was inspired with a fear which produces pious submission. He also properly calls that place the gate of heaven, on account of the manifestation of God: for, since God is placed in heaven as on His royal throne, Jacob truly declares that, in seeing God, he had penetrated into heaven. In this sense, the preaching of the gospel is called the kingdom of heaven, and the sacraments may be called the gate of heaven, because they admit us into the presence of God.

The Papists, however, foolishly misapply this passage to their temples, as if God dwelled in filthy places. But if we concede that the places which they designate by this title are not polluted with impious superstitions, yet this honor belongs to no particular place, since Christ has filled the whole world with the presence of His Deity. Only those helps to faith (as I have previously taught), by which God raises us to Himself, can be called the gates of heaven.