John Wesley on Joshua 6:26

Adjured them - Or, made them to fear; caused the people, or some in the name of all, to swear for the present and succeeding generations, and to confirm their oath by a curse. Before the Lord - That is, from God's presence, and by his sentence, as they are said to cast lots before the Lord, Josh 18:8,10, that is, expecting the design from God. He intimates, that he doth not utter this upon a particular dislike of that place, but by divine inspiration. God would have the ruins of this city remain as a standing monument of God's justice against this wicked and idolatrous people, and of his almighty power in destroying so great and strong a city by such contemptible means. Buildeth - That is, that shall attempt to build it. So this curse is restrained to the builder, but no way belongs to those who should inhabit it after it was built, as is evident from 2Kings 4:18 Luke 19:1,5. In his youngest son - That is, he shall lose all his children in the work, the first at the beginning, others in the progress of it by degrees, and the youngest in the close of it, when the gates use to be set up. This was fulfilled, 1Kings 16:34.