John Calvin Commentary Joshua 6:1

"Now Jericho was straitly shut up because of the children of Israel: none went out, and none came in." — Joshua 6:1 (ASV)

Now Jericho was straitly shut up, etc. Jericho is said to be shut up because its gates were not opened: in wartime, cities are guarded with more than usual care. It is added, by way of emphasis, that they were sealed or locked up, as if to say that the inhabitants were vigilant, so they would not be taken by surprise.

Therefore, since it could not be taken by strategy, the only hope of taking it was by open force. This serves to display the goodness of God to the children of Israel, who would have been worn out by a long and difficult siege if a substitute had not been quickly provided from heaven.

Meanwhile, there was a danger that, being forced into a corner, they might be consumed by lack and famine, as there was no way of obtaining food and provisions in a hostile region. The Lord, therefore, so that they would not become discouraged before one city, assisted them by an extraordinary miracle and opened an entrance for them by throwing down the walls, so that they might afterward have greater confidence in attacking other cities.

We now see the connection between the first two verses, in the first of which it is said that Jericho was shut up and the children of Israel were thus prevented from approaching it, while in the other God promises that He will take it for them. He makes this promise in order to prevent them from tormenting themselves with anxious thoughts. In short, God, by this easy victory at the beginning, prevents them from becoming discouraged in the future. We, at the same time, perceive the stupidity of the inhabitants, who place their walls and gates as obstacles to divine omnipotence; as if it were more difficult to break up or dissolve a few bars and beams than to dry up the Jordan.